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1

Low thrust transfer optimisation of satellites formations to heliocentric Earth trailing orbits through a gradient restoration algorithm  

Microsoft Academic Search

When dealing with mission requirements calling for highly stable gravitational and thermal environments, one of the common options always considered is that of the heliocentric Earth trailing orbits (HETO). This is the case, for instance, of the Laser Interferometer Space Antenna (LISA), a joint ESA-NASA effort aimed at detecting gravitational radiation from deep-space sources, hence testing the fundamental gravitational theories.This

J. C Bastante; A Caramagno; L. F Peñ??n; M Belló-Mora; J Rodr??guez-Canabal

2004-01-01

2

Lifetimes of Small Bodiesin Planetocentric (or Heliocentric) Orbits  

NASA Astrophysics Data System (ADS)

Small bodies left over from the formation of the planets and satellites litter the Solar System, along with the debris from more recent collisions. These bodies are removed by expulsion from heliocentric or planetocentric orbit, as well as by collisions with planets, moons, and the Sun, with characteristic lifetimes depending on their orbits. However, the rate at which a given population of objects declines cannot be described by the simple exponential law used to describe radioactive decay. On the contrary, the removal of comets and remnant planetesimals has sometimes been described as "logarithmic decay''. Our work on the fate of ejecta from Hyperion (Dobrovolskis and Lissauer 2004, Icarus 169, 462--473), as well as recent results from other satellites, suggests instead that ejecta removal is best described by a "stretched exponential'' decay law, where the particle lifetimes increase as a fractional power of the elapsed time, suggestive of a diffusion process. Statistical analysis supports this conclusion, and enables us to determine the decay parameters. The results should be valuable in several contexts, including the delivery of meteorites to Earth and the bombardment history of the planets and their moons.

Dobrovolskis, Anthony R.; Alvarellos, J. L.; Lissauer, J. J.

2006-06-01

3

Lifetimes of Small Bodies in Planetocentric (or Heliocentric) Orbits  

NASA Astrophysics Data System (ADS)

Small bodies left over from the formation of the planets and satellites litter the Solar System, along with the debris from more recent collisions. These bodies are removed by expulsion from heliocentric or planetocentric orbit, as well as by collisions with planets, moons, and the Sun, with characteristic lifetimes depending on their orbits. However, the rate at which a given population of objects declines cannot be described by the simple exponential law used to describe radioactive decay. On the contrary, the removal of comets and remnant planetesimals has sometimes been described as ``logarithmic decay". Our work on the fate of ejecta from Hyperion (Dobrovolskis and Lissauer 2004, Icarus 169, 462-473) as well as our recent results from other satellites suggests instead that ejecta removal is best described by a ``stretched exponential" decay law, where the particle lifetimes increase as a fractional power of the elapsed time, suggestive of a diffusion process. Statistical analysis suports this conclusion, and enables us to determine the decay parameters. The results should be valuable in several contexts, including the delivery of meteorites to Earth and the bombardment history of the planets and their moons. NASA's PGG grant RTOP 344-30-50-01 supported this research.

Dobrovolskis, A. R.; Alvarellos, J. L.; Lissauer, J. J.

2005-08-01

4

Optimum rendezvous transfer between coplanar heliocentric elliptic orbits using solar sail  

Microsoft Academic Search

A convenient formulation is presented for determining the effect of terminal orbit eccentricities on the steering profile of a sail spacecraft for time-optimal rendezvous transfer between coplanar heliocentric orbits. The problem is reduced to that of solving a two-point boundary value problem for a system of seven ordinary differential equations. The system is solved using the controlled random search optimization

P. V. S. Rao; R. V. Ramanan

1992-01-01

5

Lifetimes of small bodies in planetocentric (or heliocentric) orbits  

Microsoft Academic Search

Stray bodies orbiting a planet or the Sun are removed by collisions with larger objects or by expulsion from the system. However, their rate of removal generally cannot be described by the simple exponential law used to describe radioactive decay, because their effective half-life lengthens with time. Previous studies of planetesimals, comets, asteroids, meteorites, and impact ejecta from planets or

Anthony R. Dobrovolskis; José L. Alvarellos; Jack J. Lissauer

2007-01-01

6

TEMPORARY CAPTURE OF PLANETESIMALS BY A PLANET FROM THEIR HELIOCENTRIC ORBITS  

SciTech Connect

When planetesimals encounter a planet, they can be temporarily captured by the planet's gravity and orbit about it for an extended period of time before escaping from the planet's vicinity. Such a process may have played an important role in the origin of irregular satellites or the dynamical evolution of short-period comets. Using three-body orbital integration, we study the temporary capture of planetesimals by a planet from their heliocentric eccentric orbits. We examine the dependence of the orbital characteristics during temporary capture as well as the rate of capture on the pre-capture heliocentric orbital parameters. We find that typical orbital size and direction of revolution around the planet change depending on planetesimals' initial eccentricity and energy. When initial eccentricity is so small that Kepler shear dominates the relative velocity between planetesimals and the planet, temporary capture typically occurs in the retrograde direction in the vicinity of the planet's Hill sphere, while large retrograde capture orbits outside the Hill sphere are predominant for large eccentricities. Long prograde capture occurs in a very narrow range of planetesimal eccentricity and energy. We obtain the rate of temporary capture of planetesimals and find that the rate of long capture increases with increasing eccentricity at low and high eccentricities, but decreases with increasing eccentricity in intermediate values of eccentricity. We also examine the dependence of capture rate on the duration of capture and find an approximate power-law dependence.

Suetsugu, Ryo; Ohtsuki, Keiji [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan); Tanigawa, Takayuki, E-mail: ryo3088@stu.kobe-u.ac.jp [Center for Planetary Science, Kobe University, Kobe 650-0047 (Japan)

2011-12-15

7

Poisson's theorem in heliocentric variables - Conditions for the application of this theorem concerning the invariability of the major axes of planetary orbits to second order in the masses  

Microsoft Academic Search

Poisson's theorem states that there is no secular inequality in the major axis of the orbits of the planets to the first and second approximation with respect to the masses. An analytical expression for the secular term of the major axes in heliocentric coordinates in the second approximation is derived, and it is shown that in heliocentric elements this term

L. Duriez

1978-01-01

8

Regarding the Accretion of 2003 VB12 (Sedna) and Like Bodies in Distant Heliocentric Orbits  

Microsoft Academic Search

Recently, Brown et al. (2004) reported the exciting discovery of an ~800 km\\u000aradius object, (90377) Sedna, on a distant, eccentric orbit centered at ~490 AU\\u000afrom the Sun. Here we undertake a first look exploring the feasibility of\\u000aaccreting this object and its possible cohorts between 75 AU (Sedna's\\u000aperihelion distance) and 500 AU (Sedna's semi-major axis distance) from

S. Alan Stern

2004-01-01

9

Probes to the Inferior Planets - A New Dawn for NEO and IEO Detection Technology Demonstration from Heliocentric Orbits Interior to the Earth's?  

NASA Astrophysics Data System (ADS)

With the launch of MESSENGER and VENUS EXPRESS, a new wave of exploration of the inner solar system has begun. Noting the growing number of probes to the inner solar system, it is proposed to connect the expertise of the respective spacecraft teams and the NEO and IEO survey community to best utilize the extended cruise phases and to provide additional data return in support of pure science as well as planetary defence. Several missions to Venus and Mercury are planned to follow in this decade. Increased interest in the inferior planets is accompanied by several missions designed to study the Sun and the interplanetary medium (IPM) from a position near or in Earth orbit, such as the STEREO probes and SDO. These augment established solar observation capabilities at the Sun-Earth L1 Lagrangian point such as the SOHO spacecraft. Thus, three distinct classes of spacecraft operate or observe interior to Earth's orbit. All these spacecraft carry powerful multispectral cameras optimized for their respective primary targets. MESSENGER is scheduled to end its six-year interplanetary cruise in March 2011 to enter Mercury orbit, but a similarly extended cruise with several gravity-assists awaits the European Mercury mission BEPICOLOMBO. Unfortunately, the automatic abort of the orbit insertion manoeuvre has also left AKATSUKI (a.k.a. Venus Climate Orbiter (VCO), Planet-C) stranded in heliocentric orbit. After an unintended fly-by, the probe will catch up with Venus in approximately six years. Meanwhile, it stays mostly interior to Venus in a planet-leading orbit. In addition to the study of comets and their interaction with the IPM, observations of small bodies akin to those carried out by outer solar system probes are occasionally attempted with the equipment available. The study of structures in the interplanetary dust (IPD) cloud has been a science objective during the cruise phase of the Japanese Venus probe AKATSUKI from Earth to Venus. IPD observations in the astronomical H-band (1.65 ?m) are supported by its IR2 camera down to 1.5 ?W/m2sr in single 2 minute exposures. In the same setting, point sources of 13 mag can be detected. Obviously, a number of large asteroids exceed this threshold. The EARTHGUARD-I study, completed in 2003 by the DLR Institute of Planetary Research and Kayser-Threde under ESA contract, proposed a dedicated steerable 020...35 cm telescope and CCD camera payload on a probe to the inner solar system, to detect Near-Earth and Inner-Earth Objects (NEOs, IEOs) in favourable opposition geometry. A ride- share on a Mercury orbiter and a dedicated low-thrust propulsion spacecraft to a heliocentric 0.5 AU orbit were studied. A similar-sized telescope is presently being developed for the ASTEROIDFINDER satellite of DLR. Therefore, the technical feasibility of a number of asteroid observation scenarios involving spacecraft and targets interior to Earth's orbit is assessed based on the latest available spacecraft information and asteroid population models. A rough estimate of the required effort in terms of ground-based spacecraft operations and on-board resources is given for selected representative scenarios.

Grundmann, J. T.; Mottola, S.; Drentschew, M.; Drobczyk, M.; Kahle, R.; Maiwald, V.; Quantius, D.; Zabel, P.; Van Zoest, T.

2011-11-01

10

Comprehensive investigation of the dynamics of micron and submicron lunar ejecta in heliocentric space  

SciTech Connect

The forces which act on micron and submicron dust particles in interplanetary space are studied in detail. Particular attention is given to Mie scattering theory as it applies to the calculation of the force due to radiation pressure. All of the forces are integrated into a computer model to study the heliocentric orbits of lunar ejecta. It is shown that lunar ejecta contribute to a geocentric dust cloud, as well as to a heliocentric dust belt.

Hargrave, A.D.

1984-01-01

11

Planetocentric versus heliocentric impacts in the Jovian and Saturnian satellite system  

Microsoft Academic Search

Readily applicable equations are derived for calculating the impact velocities, collision intervals, and cumulative crater frequencies in a satellite system for planetocentric and heliocentric impactors. Observed cumulative crater frequencies in the Saturnian satellite system and a sometimes observed lack of apex-antapex asymmetry of crater frequencies favor crater-producing projectiles orbiting initially in elliptic orbits round the parent planet (planetocentric impactors). On

G. P. Horedt; G. Neukum

1984-01-01

12

The cometary outbursts at large heliocentric distances  

Microsoft Academic Search

A model is presented explaining changes in cometary brightness during an outburst at large heliocentric distances. It is shown that a combination of the following effects can explain the main characteristics of outburst at large heliocentric distances: the specific exothermic processes in cometary nucleus (as the HCN polymerisation and the crystallization of the water amorphous ice, connected with the ejection

P. Gronkowski; J. Smela

1998-01-01

13

Optimal three-dimensional heliocentric solar-sail rendezvous transfer trajectories  

Microsoft Academic Search

This study is concerned with the problem of optimization of the control, in the sense of high speed of response, for minimum time rendezvous transfer of sail-spacecraft between heliocentric, inclined, elliptic orbits. The angles defining the orientation of the sail (assumed to be perfectly reflecting and flat) with respect to sunlight are the control variables. The analysis employs a two-body

P. V. Subba Rao; R. V. Ramanan

1993-01-01

14

A comprehensive investigation of the dynamics of micron and submicron lunar ejecta in heliocentric space  

Microsoft Academic Search

The forces which act on micron and submicron dust particles in interplanetary space are studied in detail. Particular attention is given to Mie scattering theory as it applies to the calculation of the force due to radiation pressure. All of the forces are integrated into a computer model to study the heliocentric orbits of lunar ejecta. It is shown that

A. D. Hargrave

1984-01-01

15

Planar heliocentric roto-translatory motion of a spacecraft with a solar sail of complex shape  

Microsoft Academic Search

A complete treatment of the general motion of rotation and translation of a solar-sail spacecraft is proposed for the non-flat sail of complex shape. The planar heliocentric roto-translatory motion is considered, orbit-rotational coupling in the problem of altitude and orbital sail motion is investigated for the two-folding sail formed by two unequal reflective rectangular plates oriented at a right angle.

S. N. Kirpichnikov; E. S. Kirpichnikova; E. N. Polyakhova; A. S. Shmyrov

1995-01-01

16

Proof-of-Concept Trajectory Designs for a Multi-Spacecraft, Low-Thrust Heliocentric Solar Weather Buoy Mission.  

National Technical Information Service (NTIS)

A new solar weather mission has been proposed, involving a dozen or more small spacecraft spaced at regular, constant intervals in a mutual heliocentric circular orbit between the orbits of Earth and Venus. These solar weather buoys (SWBs) would carry ins...

R. Muller H. Franz C. Roberts D. Folta

2005-01-01

17

Ancient Greek Heliocentric Views Hidden from Prevailing Beliefs?  

NASA Astrophysics Data System (ADS)

We put forward the working hypothesis that the heliocentric, rather than the geocentric view, of the Solar System was the essential belief of the early Greek philosophers and astronomers. Although most of them referred to the geocentric view, it is plausible that the prevalent religious beliefs about the sacred character of the Earth as well as the fear of prosecution for impiety (asebeia) prevented them from expressing the heliocentric view, even though they were fully aware of it. Moreover, putting the geocentric view forward, instead, would have facilitated the reception of the surrounding world and the understanding of everyday celestial phenomena, much like the modern presentation of the celestial sphere and the zodiac, where the Earth is at the centre and the Sun makes an apparent orbit on the ecliptic. Such an ingenious stance would have set these early astronomers in harmony with the dominant religious beliefs and, at the same time, would have helped them to 'save the appearances', without sacrificing the essence of their ideas. In Hellenistic and Roman times, the prevailing view was still the geocentric one. The brilliant heliocentric theory advanced by Aristarchos in the early third century B.C. was never established, because it met with hostility in Athens - Aristarchos was accused of impiety and faced the death penalty. The textual evidence suggests that the tight connection which existed between religion and the city-state (polis) in ancient Greece, and which led to a series of impiety trials against philosophers in Athens during the fifth and fourth centuries B.C., would have made any contrary opinion expressed by the astronomers seem almost a high treason against the state.

Liritzis, Ioannis; Coucouzeli, Alexandra

2008-03-01

18

Rigorous treatment of the heliocentric motion of stars  

Microsoft Academic Search

The transformation of star heliocentric coordinates from one epoch to another involves precession, nutation, and the apparent motion which is due to space motion in an inertial reference frame. Attention is presently given to a theory of the apparent heliocentric motion which handles both the perspective effects and the effects due to relativity in a rigorous fashion. The observational equivalents

P. Stumpff

1985-01-01

19

Orbital  

NASA Astrophysics Data System (ADS)

ORBITAL requires the following software, which is available for free download from the Internet: Netscape Navigator, version 4.75 or higher, or Microsoft Internet Explorer, version 5.0 or higher; Chime Plug-in, version compatible with your OS and browser (available from MDL).

Hanson, Robert M.

2003-06-01

20

Heliocentric Distance Dependence of the Interplanetary Magnetic Field.  

National Technical Information Service (NTIS)

Recent and ongoing planetary missions have provided extensive observations of the variations of the Interplanetary Magnetic Field (IMF) both in time and with heliocentric distance from the sun. Large time variations in both the IMF and its fluctuations we...

K. W. Behannon

1977-01-01

21

3D high-speed escape heliocentric trajectories by all-metallic-sail low-mass sailcraft  

Microsoft Academic Search

Considering a photon solar-sail spacecraft with a lightness number in the range [12–1) (all-metallic sail), this paper analyses a class of heliocentric trajectories, characterized by orbital angular-momentum reversal, delivering a considerable cruise speed (10–20 AU\\/yr) and allowing a sailcraft to access any celestial latitude [??2, +?2], depending primarily on the perihelion distance. It is found out that, if the lightness

Giovanni Vulpetti

1996-01-01

22

Heliocentric distance dependence of the interplanetary magnetic field  

Microsoft Academic Search

Recent and ongoing planetary missions have provided and are continuing to provide extensive observations of the variations of the interplanetary magnetic field (IMF) both in time and with heliocentric distance from the sun. Large time variations in both the IMF and its fluctuations are observed. These are produced predominantly by dynamical processes in the interplanetary medium associated with stream interactions.

Kenneth W. Behannon

1978-01-01

23

Pioneer 10 studies of interplanetary shocks at large heliocentric distances  

Microsoft Academic Search

Pioneer 10 Ames plasma analyzer data collected in the 6.1 to 12.6 AU range of heliocentric distances (November 1974 to April 1977) have been examined for interplanetary shock waves. Eighteen shock signatures have been identified, with four of these being of the reverse type and the remainder the forward type. Sonic Mach numbers in the range from 3 to 10

J. D. Mihalov; J. H. Wolfe

1979-01-01

24

A general planetary theory in elliptical heliocentric variables  

Microsoft Academic Search

The work proposes an analytical theory that generalizes Verrier's classical theory. The motion of planets about the sun is described in the neighborhood of uniform circular coplanar motions by elliptical osculating heliocentric elements. The variations of these elements are expressed in series with periodic terms: secular terms (with periods greater than 50,000 years), and short-period terms whose amplitudes are functions

L. Duriez

1979-01-01

25

Heliocentric distance dependence of the interplanetary magnetic field  

Microsoft Academic Search

Recent and ongoing planetary missions have provided extensive observations of the variations of the Interplanetary Magnetic Field (IMF) both in time and with heliocentric distance from the sun. Large time variations in both the IMF and its fluctuations were observed. These are produced predominantly by dynamical processes in the interplanetary medium associated with stream interactions. Magnetic field variations near the

K. W. Behannon

1977-01-01

26

Ancient Greek Heliocentric Views Hidden from Prevailing Beliefs?  

Microsoft Academic Search

We put forward the working hypothesis that the heliocentric, rather than the geocentric view, of the Solar System was the essential belief of the early Greek philosophers and astronomers. Although most of them referred to the geocentric view, it is plausible that the prevalent religious beliefs about the sacred character of the Earth as well as the fear of prosecution

Ioannis Liritzis; Alexandra Coucouzeli

2008-01-01

27

Gas Activity in Comets at Large Heliocentric Distances  

NASA Astrophysics Data System (ADS)

Observations of comets and associated cometary activity as a function of heliocentric distance are a useful constraint on the various outgassing mechanisms. For heliocentric distances < 3 AU, the assumed primary driver of cometary activity is H2O sublimation. Activity at heliocentric distances > 3 AU has been observed for a number of comets, and debates continue as to if the activity is driven by an amorphous to crystalline H2O ice transition, or sublimation of other highly volatile species such as CO. As part of a narrowband imaging program utilizing the Hale-Bopp cometary filters and a spectroscopy program at the 2.3-m Bok Telescope, we present results on the gas and dust production of 7 comets with comae at heliocentric distances ranging from 3.34 to 6.72 AU. From this sample of objects at distances > 3 AU, we also present CN, C2, and C3 gas production values for 3 comets discovered in 2012 in order to classify them as either carbon "normal" or carbon-depleted.

Ryan, Erin L.; Woodward, C. E.

2012-10-01

28

Structure of the Solar Wind at Large Heliocentric Distances: CIRs and their Successors.  

National Technical Information Service (NTIS)

Co-rotating interaction regions (CIRs) and their associated shock pairs are dominant structures in the solar wind between the heliocentric distances of 2 and 8 AU. At larger heliocentric distances, these structures undergo a qualitative change. Shocks dec...

P. R. Gazis

1997-01-01

29

Structure of the Solar Wind at Large Heliocentric Distances: CIRs and their Successors.  

National Technical Information Service (NTIS)

Co-rotating interaction regions (CIRs) and their associated shock pairs are dominant structures in the solar wind between the heliocentric distances of 2 and 8 AU. At larger heliocentric distances, these structures undergo a qualitative change. Shocks dec...

P. R. Gazis

1999-01-01

30

Brightness of long-period comets observed at large heliocentric distances (III. The computer catalogue for 1959 - 1976)  

NASA Astrophysics Data System (ADS)

The paper is a compilation of 3327 magnitude estimates of 21 long-period comets observed at the heliocentric distances larger than 2.5 AU with the well determined orbits which passed the perihelion from 1959 to 1976. This is the third part of the catalogue of long-period comets. The first two parts (covering 1861-1957) were published before. The catalogue can serve as a supplement to the short-period CLICC/A catalolgue compiled by Kamél and ICQ archive compiled by Green et al. The catalogue exists only in computer version and can be downloaded from the author's www homepage.

Svore?, J.

2002-11-01

31

Shock-associated energetic proton events at large heliocentric distances  

Microsoft Academic Search

Enhancements of energetic protons (> or approx. =0.5 MeV) in association with forward-reverse shock pairs have been observed at large heliocentric distances. An interpretation of the time profiles of these events is offered in terms of a model of solar wind stream structure. Persistent sweeping of energetic particles by each shock front and their banking-up by reflection lead to the

I. D. Palmer; J. T. Gosling

1978-01-01

32

Dust emission from comets at large heliocentric distances  

Microsoft Academic Search

Possible mechanisms for the production of the extended dust coma observed in comet Bowell (1980b) at the large heliocentric distance of 7.17 AU are considered. It is concluded that a plausible mechanism is electrostatic blow-off of fine, loose dust from an electrically charged H2O dominated nucleus, as recently proposed by Mendiset al. (1981). Of all the other processes considered, dust

Harry L. F. Houpis; D. A. Mendis

1981-01-01

33

Activity of comets at large heliocentric distances pre-perihelion  

Microsoft Academic Search

We present observational data for two long-period and three dynamically new comets observed at heliocentric distances between 5.8 to 14.0 AU. All of the comets exhibited activity beyond the distance at which water ice sublimation can be significant. We have conducted experiments on gas-laden amorphous ice samples and show that considerable gas emission occurs when the ice is heated below

K. J. Meech; J. Pittichová; A. Bar-Nun; G. Notesco; D. Laufer; O. R. Hainaut; S. C. Lowry; D. K. Yeomans; M. Pitts

2009-01-01

34

On the Provability of Heliocentrism. I. Ole Roemer and the Finite Speed of Light  

NASA Astrophysics Data System (ADS)

This paper describes observational support of heliocentrism during the late Renaissance. Initiated by Galileo's clues from telescopic sightings, the first indirect quantitative support for the heliocentric doctrine resulted from accurate eclipse timings of the , made possible by breakthroughs in technology (telescope optics and the pendulum clock) and driven by the quest for longitude at sea and on land. The resulting discovery of Olaus Roemer that the velocity of light is finite, is an indirect argument supporting heliocentrism.

Sterken, Christiaan

2007-10-01

35

Forbidden oxygen lines in comets at various heliocentric distances  

NASA Astrophysics Data System (ADS)

We present a study of the three forbidden oxygen lines [OI] located in the optical region - i.e., 5577.339 Å (the green line), 6300.304 Å and 6363.776 Å (the two red lines) - in order to better understand the production of these atoms in cometary atmospheres. The analysis is based on 48 high-resolution and high signal-to-noise spectra collected with UVES at the ESO VLT between 2003 and 2011 referring to 12 comets of different origins observed at various heliocentric distances. The flux ratio of the green line to the sum of the two red lines is evaluated to determine the parent species of the oxygen atoms by comparison with theoretical models. This analysis confirms that, at about 1 AU, H2O is the main parent molecule producing oxygen atoms. At heliocentric distances >2.5 AU, this ratio changes rapidly, an indication that other molecules are starting to contribute. The most abundant species after H2O in the coma, CO and CO2, are good candidates, and the ratio is used to estimate their abundances. We found that the CO2 abundance relative to H2O in comet C/2001 Q4 (NEAT) observed at 4 AU can be as high as ~70%. The intrinsic widths of the oxygen lines were also measured. The green line is on average about 1 km s-1 broader than the red lines, while the theory predicts that the red lines are broader. This might be due to the nature of the excitation source or to a contribution of CO2 as the parent molecule of the 5577.339 Å line. At 4 AU, we found that the width of the green and red lines in comet C/2001 Q4 are the same, which could be explained if CO2 becomes the main contributor to the three [OI] lines at high heliocentric distances. Based on observations made with ESO Telescope at the La Silla Paranal Observatory under programs ID 268.C-5570, 270.C-5043, 073.C-0525, 274.C-5015, 075.C-0355, 080.C-0615, 280.C-5053, 086.C-0958, and 087.C-0929.

Decock, A.; Jehin, E.; Hutsemékers, D.; Manfroid, J.

2013-07-01

36

Heliocentric distance and temporal dependence of the interplanetary density-magnetic field magnitude correlation  

Microsoft Academic Search

The Helios, IMP 8, ISEE 3, and Voyager 2 spacecraft are used to examine the solar cycle and heliocentric distance dependence of the correlation between density n and magnetic field magnitude B in the solar wind. previous work had suggested that this correlation becomes progressively more negative with heliocentric distance out to 9.5 AU. Here they show that this evolution

D. A. Roberts

1990-01-01

37

Heliocentric zoning of the asteroid belt by aluminum-26 heating  

SciTech Connect

The dependence of asteroid spectral class (and inferred composition and thermal history) on heliocentric radius has been held to be the result of heating by a solar energy source, most likely electrical induction, during the formation of the planetary system. Such variations in thermal history can be more simply explained by the presence of different amounts of the radionuclide aluminum-26, whose decay products are observed in meteorites, in planetesimals. These differences occurred naturally as a function of the increasing amount of time required to accrete objects farther from the sun, during which aluminum-26 decayed from its initial concentration in the solar nebula. Both theory and isotopic evidence suggest that increases in accretion time across the asteroid belt are of order several half-lives of aluminum-26, which is sufficient to produce the inferred differences in thermal history. 35 refs., 1 fig.

Grimm, R.E. (Arizona State Univ., Tempe (United States)); McSween, H.Y. Jr. (Univ. of Tennessee, Knoxville (United States))

1993-01-29

38

Application of the heliocentric potential to aircraft dosimetry.  

PubMed

The heliocentric potential is the result of a steady-state solution to the diffusion equation of cosmic rays through the solar wind. The counting rate of any high-latitude, ground-level neutron monitor can be used to determine this potential, which will return cosmic ray spectra in real time. These spectra are routinely used to determine the radiation dose rate to which air crew are exposed during the precise hours of a flight, including the effects of quick decreases and Forbush decreases. Further, it has been used in an effort to calculate the radiation dose rate to air crew during an energetic solar particle event, as the cosmic ray background before the event must be determined. An alternate approach is to use the deceleration potential, which assumes a significant time-dependence of cosmic rays through the heliosphere. However, the theory behind it does not account for the behaviour of ground-level neutron monitors. PMID:16604656

O'Brien, Keran; Felsberger, Ernst; Kindl, Peter

2005-01-01

39

Pioneer10 observation of the solar wind proton temperature heliocentric gradient  

Microsoft Academic Search

Solar wind isotropic proton temperatures as measured out to 12.2 AU heliocentric distance by the Ames plasma analyzer aboard Pioneer-10 are presented as consecutive averages over three Carrington solar rotations and discussed. The weighted least-squares fit of average temperature to heliocentric radial distance, R, yields the power law R-0.52. These average proton temperatures are not correlated as well with Pioneer-10's

J. D. Mihalov; J. H. Wolfe

1978-01-01

40

The trend of production rates with heliocentric distance for comet P\\/Halley  

Microsoft Academic Search

Comet P\\/Halley was observed spectroscopically in the wavelength range 5200-10,400 A during 10 observing runs, roughly a month apart from 1985 August 28 to 1986 June 6. The observations span a heliocentric distance from 0.73 to 2.52 AU. This data set is analyzed to determine the course of the production rate with heliocentric distance for C2, NH2, CN, and the

U. Fink

1994-01-01

41

The heliocentric system from the Orphic Hymns and the Pythagoreans to emperor Julian  

NASA Astrophysics Data System (ADS)

The evolution of the heliocentric theory in the antiquity has been analyzed, from the first seeds in the Orphic Hymns to the emperor Julian, also called "the Apostate" in the 4th century A.D. In particular the Orphic Hymns, views of Pythagoreans, as well as the heliocentric ideas of Philolaus of Croton, Icetas, Ecphantus, Heraclides of Pontos, Anaximander, Seleucus of Seleucia, Aristarchus of Samos and Emperor Julian were analyzed.

Theodossiou, Efstratios; Dacanalis, Aris; Dimitrijevi?, Milan, S.; Mantarakis, Petros

42

Orbit Design for General Relativity Experiments: Heliocentric and Mercury-centric Cases  

Microsoft Academic Search

Tracking a spacecraft near the Sun provides unique opportunities to estimate gravity param- eters and to test fundamental theories of physics. We develop a detailed covariance analysis of such trajectories, analyzing the uncertainty distribution of the flrst order Parameterized Post- Newtonian parameters (? and fl) and the solar quadrupole (J2) moment based on radiometric measurements. Our analysis includes the efiect

Ryan S. Park; Daniel J. Scheeres; Giacomo Giampieri; James M. Longuski; Ephraim Fischbach

43

The Kepler Mission: A wide-field transit search for terrestrial planets  

Microsoft Academic Search

The Kepler Mission is a NASA Discovery mission which will continuously monitor the brightness of at least 100,000 main sequence stars, to detect the transits of terrestrial and larger planets. It is scheduled to be launched in 2007 into an Earth-trailing heliocentric orbit. It is a wide-field photometer with a Schmidt-type telescope and array of 42 CCDs covering the 100

Gibor Basri; William J. Borucki; David Koch

2005-01-01

44

Detection of several daemon populations in earth-crossing orbits  

Microsoft Academic Search

Experiments on scintillator-based detection of negative dark electric matter objects, daemons, representing Planckian supermassive (about 2 ? 10 m 5 v g) particles that were detected in March 2000 as populating near-Earth, almost circular heliocentric orbits (NEACHOs), are being continued. The NEACHO objects hit the Earth with a velocity of about 10-15 v km v s m 1 . The

E. M. Drobyshevski; M. V. Beloborodyy; R. O. Kurakin; V. G. Latypov; K. A. Pelepelin

2003-01-01

45

From Pythagoreans to Kepler: the dispute between the geocentric and the heliocentric systems  

NASA Astrophysics Data System (ADS)

Some ancient Greek philosophers and thinkers questioned the geocentric system and proposed instead a heliocentric system. The main proponents of this view - which was seen as heretical at the time - are believed to have been the Pythagoreans Philolaos, Heraclides, Hicetas, and Ecphantos, but mainly Aristarchos of Samos, who placed the Sun in the position of the "central fire" of the Pythagoreans. The geocentric system, reworked by Claudius Ptolemaeus (Ptolemy), was the dominant one for centuries, and it was only during the sixteenth century that the Polish monk-astronomer, Copernicus, revisited the ancient Greek heliocentric views and became the new champion of the theory that we all accept today.

Theodossiou, E.; Danezis, E.; Manimanis, V. N.; Kalyva, E.-M.

2002-06-01

46

Impactors on Saturn's Regular Satellites: Heliocentric vs. Planetocentric  

NASA Astrophysics Data System (ADS)

Voyager-era scientists concluded that Saturn's moons were struck by at least two impactor populations. Population I impactors - most likely "comets" orbiting the Sun - formed most of the larger and older craters, while Population II impactors - possibly Saturn-orbiting ejecta from impacts on satellites - produced most of the smaller and younger craters [1]. Present-day dynamical models predict that "ecliptic comets," which likely originate in the Kuiper Belt/Scattered Disk, are the primary impactors on the regular satellites of the giant planets [2]. However, these models predict vastly more craters on the leading faces of synchronously rotating moons than on the trailing faces [3]; such asymmetries are not observed. The answer to this riddle might be nonsynchronous rotation; crater saturation; or the putative Population II impactors, which should not create strong asymmetries [4]. We focus on Cassini measurements and interpretation of the crater size-frequency distributions on Mimas, Enceladus, and Rhea. Because Mimas and Enceladus have weak gravities, they are excellent sources of Saturn-orbiting ejecta, which usually come back to strike their parent moons, making "sesquinary" craters. Impacts on weightier Rhea are more apt to make traditional secondary craters [5]. We will apply ejecta models [6] to quantify the importance of sesquinary craters on the saturnian moons. The biggest uncertainty is the size of the ejecta [7]. We thank the CDAP program for support. References: [1] Dones L., et al., in Saturn from Cassini-Huygens, pp. 613-635 (2009). [2] Zahnle K., et al., Icarus 163, 263-289 (2003). [3] Zahnle K. et al., Icarus 153, 111-129 (2001). [4] Alvarellos J., et al., Icarus 178, 104-123. [5] Bierhaus E. et al., Lunar Planet. Sci. 42 (2011). [6] Housen K.R., Holsapple, K.A., Icarus 211, 856-875 (2011). [7] Zahnle K. et al., Icarus 194, 660-674 (2008).

Dones, Henry C. Luke; Bierhaus, E. B.; Zahnle, K. J.; Alvarellos, J. L.

2011-04-01

47

On the gradients of ACR oxygen at intermediate heliocentric distances: Ulysses\\/SOHO results  

Microsoft Academic Search

During 1997 and up to the present time, the heliocentric position of the Ulysses spacecraft has changed only slowly in distance and latitude, being close to the equator at a distance of ?5 AU. This period provides an excellent opportunity to observe the evolution of the Anomalous Cosmic Ray (ACR) spectrum at a location intermediate between 1 AU and the

R. G Marsden; T. R Sanderson; C. Tranquille; K. J Trattner; A. Anttila; J. Torsti

1999-01-01

48

Pioneer 10 Observation of the Solar Wind Proton Temperature Heliocentric Gradient.  

National Technical Information Service (NTIS)

Solar wind isotropic proton temperatures as measured out to 12.2 AU heliocentric distance by the Ames plasma analyzer aboard Pioneer 10 are presented as consecutive averages over three Carrington solar rotations and discussed. The weighted least-squares f...

J. D. Mihalov J. H. Wolfe

1978-01-01

49

The possible formation of a hydrogen coma around comets at large heliocentric distances  

Microsoft Academic Search

An observational test, the detection of a hydrogen coma around comets at large heliocentric distances, is proposed for determining whether comets were formed by the agglomeration of unaltered, ice-coated, interstellar grains. Laboratory experiments showed that amorphous water ice traps H2, D2, and Ne below 20 K and does not release them completely until the ice is heated to 150 K.

A. Bar-Nun; D. Prialnik

1988-01-01

50

On the brightness variations of comet Halley at large heliocentric distances  

Microsoft Academic Search

Sporadic variations of its intrinsic brightness of up to 500%, with time scales as short as a few hours, has been exhibited by Halley's comet at large heliocentric distances (11-8 AU). It is shown that many of these brightness enhancements are closely correlated to the encounter of high-speed solar wind streams by the comet. It is proposed that during such

K. R. Flammer; B. Jackson; D. A. Mendis

1986-01-01

51

Pioneer and voyager observations of the solar wind at large heliocentric distances and lattitudes  

Microsoft Academic Search

The Pioneer 10, 11, and Voyager 2 spacecraft are well suited for exploring spatial gradients in the distant solar wind. Between 1984 and 1986 Pioneer 11 and Voyager 2 were located at nearly the same heliocentric distance (approx. =20 AU) and longitude but were widely separated in latitude; Pioneer 11 was at a heliographic latitude of greater than or equal

P. R. Gazis; J. D. Mihalov; A. Barnes; A. J. Lazarus; E. J. Smith

1989-01-01

52

Narrowband Photometry of Comet P\\/Halley: Variation with Heliocentric Distance, Season, and Solar Phase Angle  

Microsoft Academic Search

Narrowband filter photometry of Comet P\\/Halley from 109 nights in 1985, 1986, and 1987 is analyzed to discern the comet's variation in activity with changing heliocentric distance and season. The scattering phase function of dust in the coma is also investigated. Asymmetry about perihelion in the production of gas and dust is confirmed. However, we find the asymmetry to be

David G. Schleicher; Robert L. Millis; Peter V. Birch

1998-01-01

53

The amplitudes of interplanetary fluctuations: Stream structure, heliocentric distance, and frequency dependence  

Microsoft Academic Search

The authors present a study of the heliocentric distance, frequency, and stream structure dependence of the amplitudes of interplanetary fluctuations in the velocity and magnetic field from 0.3 to nearly 20 AU and for spacecraft-frame periods of 10 days to a few hours. The results constrain theories of the acceleration of the solar wind and of the evolution of fluctuation

D. A. Roberts; M. L. Goldstein; L. W. Klein

1990-01-01

54

Pioneer 10 observations of zodiacal light brightness near the ecliptic: Changes with heliocentric distance  

Microsoft Academic Search

Sky maps made by the Pioneer 10 Imaging Photopolarimeter (IPP) at sun-spacecraft distances from 1 to 3 AU have been analyzed to derive the brightness of the zodiacal light near the ecliptic at elongations greater than 90 degrees.The change in zodiacal light brightness with heliocentric distance is compared with models of the spatial distribution of the dust. Use of background

M. So HANNER; J. Go SPARROW; J. L. WEINBERG; D. Eo BEESON

55

Solar wind structure at large heliocentric distances: An interpretation of Pioneer 10 observations  

Microsoft Academic Search

Examination of hourly values of the solar wind speed observed by the Pioneer 10 spacecraft beyond a heliocentric distance of 4 AU reveals (1) a prevalent 'sawtoothlike' speed-time profile, most speed fluctuations displaying a rapid rise and a much slower decline, and (2) the nearly universal appearance of abrupt (on the 1-hour time resolution of these data) changes in the

A. J. Hundhausen; J. T. Gosling

1976-01-01

56

Heliocentric distance and temporal dependence of the interplanetary density-magnetic field magnitude correlation  

SciTech Connect

The Helios, IMP 8, ISEE 3, and Voyager 2 spacecraft are used to examine the solar cycle and heliocentric distance dependence of the correlation between density n and magnetic field magnitude B in the solar wind. previous work had suggested that this correlation becomes progressively more negative with heliocentric distance out to 9.5 AU. Here they show that this evolution is not a solar cycle effect, and that the correlations become even more strongly negative at heliocentric distances larger than 9.5 AU. There is considerable variability in the distributions of the correlations at a given heliocentric distance, but this is not simply related to the solar cycle. Examination of the evolution of correlations between density and speed suggests that most of the structures responsible for evolution in the anticorrelation between n and B are not slow-mode waves, but rather pressure balance structures. The latter consist of both coherent structures such as tangential discontinuities and the more generally pervasive pseudosound which may include the coherent structures as a subset.

Roberts, D.A. (NASA Goddard Space Flight Center, Greenbelt, MD (United States))

1990-02-01

57

Science-philosophy relation and the prevalence of the heliocentric theory  

Microsoft Academic Search

The relation between philosophy and science has passed from many phases in history and still is an interesting topic. The value of falsifiability (or refutability) in science was stressed by Popper. Here, as a paradigm, the juxtaposition of the Earth-centered view of the universe and the prevalence of the heliocentric theory is examined. A new physics appeared in the West

E. Theodossiou; V. N. Manimanis; E. Danezis

2010-01-01

58

On the Provability of Heliocentrism. II. Leon Foucault and the Rotation of the Earth  

Microsoft Academic Search

This paper deals with the experimental provability of heliocentrism from the scientific Renaissance in the beginning of the 17th century, till the Industrial Revolution of the 1850s. Foucault's famous pendulum demonstration is documented. We underline the importance of high accuracy of observations, the interdependence of hypotheses and theories, the impact of technological breakthroughs, the role of serendipity, the importance of

Christiaan Sterken

2007-01-01

59

From Phytagoreans to Kepler: the dispute between the geocentric and the heliocentric systems  

Microsoft Academic Search

Some ancient Greek philosophers and thinkers questioned the geocentric system and proposed instead a heliocentric system. The main proponents of this view - which was seen as heretical at the time - are believed to have been the Pythagoreans Philolaos, Heraclides, Hicetas, and Ecphantos, but mainly Aristarchos of Samos, who placed the Sun in the position of the \\

E. Theodossiou; E. Danezis; V. N. Manimanis; E.-M. Kalyva

2002-01-01

60

The heliocentric radial gradient in cosmic ray density and the `swinson' sidereal time variation  

Microsoft Academic Search

The sidereal time variation reported by Swinson depends on the existence of a heliocentric radial gradient of cosmic ray density in the rigidity range <~ 100 GV and appears because of the inclination of the axis of rotation of the Earth to the normal to the ecliptic plane. It is sensitive to the polarity of the interplanetary magnetic field. Meson

D. M. Thomson

1973-01-01

61

The trend of production rates with heliocentric distance for comet P/Halley  

NASA Astrophysics Data System (ADS)

Comet P/Halley was observed spectroscopically in the wavelength range 5200-10,400 A during 10 observing runs, roughly a month apart from 1985 August 28 to 1986 June 6. The observations span a heliocentric distance from 0.73 to 2.52 AU. This data set is analyzed to determine the course of the production rate with heliocentric distance for C2, NH2, CN, and the continuum. The effect of changing the Haser scale lengths and their heliocentric distance dependence is examined. The production rate ratios to water change only in a minor way, but the absolute values of the production rates are more severely affected. Fluorescent efficiencies, or g-factors for the CN red system are calculated, and band intensity ratios for NH2 and CN are presented. Using presently available fluorescence efficiencies and Haser scale lengths, mixing ratios for the parents of C2, CN, and NH2 with respect to water are: 0.34 +/- 0.07%, 0.15 +/- 0.04%, and 0.13 +/- 0.05%. It is found that these mixing ratios are essentially constant over the heliocentric distance range of the observations, implying a rather uniform nucleus and uniform outgassing characteristics, although there are indications of smaller scale day-to-day variations. The results provide strong observational confirmation that water evaporation controls the activity of the comet over the distance range studied. Continuum values Af rho are determined, and their ratios to QH2O are found to have a clear dependence with heliocentric distance approximately r-1.0 with a post-perihelion enhancement. No correlation of the production rate ratios with light curve of P/Halley were found, nor was there any correlation of the C2 or CN production with the dust.

Fink, U.

1994-03-01

62

Heliocentric Dependence of the Sodium Emission of Comet 153P\\/Ikeya-Zhang  

Microsoft Academic Search

A low-dispersion spectroscopic monitor of comet 153P\\/Ikeya-Zhang was carried out from 2002 February through May. The sodium emission was derived mainly during March, when the heliocentric distance of the comet was between 0.511 and 0.764 AU. The number of the produced sodium atoms relative to the total cross section of dust grains follows a power law of r-5.1+\\/-1.0, where r

Jun-ichi Watanabe; Hideyo Kawakita; Reiko Furusho; Mitsugu Fujii

2003-01-01

63

Near-IR internetwork spectro-polarimetry at different heliocentric angles  

Microsoft Academic Search

The analysis of near infrared spectropolarimetric data at the internetwork at\\u000adifferent regions on the solar surface could offer constraints to reject\\u000acurrent modeling of these quiet areas.\\u000a We present spectro-polarimetric observations of very quiet regions for\\u000adifferent values of the heliocentric angle for the Fe I lines at 1.56 micron,\\u000afrom disc centre to positions close to the limb.

M. Jesus Martinez Gonzalez; A. Asensio Ramos; A. Lopez Ariste; R. Manso Sainz

2007-01-01

64

Comet 67P\\/Churyumov-Gerasimenko at a large heliocentric distance  

Microsoft Academic Search

Aims: The Jupiter family comet 67P\\/Churyumov-Gerasimenko (67P\\/C-G) is the target comet of ESA's ROSETTA mission. A detailed portrait of this comet has been drawn from observations around perihelion, but what needs to be enhanced is the description of the comet's behaviour at large heliocentric distance. It is not only important for planning the rendezvous of the ROSETTA spacecraft with the

C. Tubiana; L. Barrera; M. Drahus; H. Boehnhardt

2008-01-01

65

Antarctic polar plateau vertical electric field variations across heliocentric current sheet crossings  

Microsoft Academic Search

A superposed epoch analysis of variations of the vertical electric field measured at Vostok (78.5°S, 107°E; magnetic latitude 83.6°S) during 1998–2002 heliocentric current sheet (HCS) crossings yields no significant variation other than an association imposed by polar-cap potential differences above the site. This result contradicts published reports of a reduction ?15% in electric field 1–3 days after HCS crossings, an

G. B. Burns; B. A. Tinsley; A. R. Klekociuk; O. A. Troshichev; A. V. Frank-Kamenetsky; M. L. Duldig; E. A. Bering; J. M. Clem

2006-01-01

66

Antarctic polar plateau vertical electric field variations across heliocentric current sheet crossings  

Microsoft Academic Search

A superposed epoch analysis of variations of the vertical electric field measured at Vostok (78.5°S, 107°E; magnetic latitude 83.6°S) during 1998 2002 heliocentric current sheet (HCS) crossings yields no significant variation other than an association imposed by polar-cap potential differences above the site. This result contradicts published reports of a reduction ˜15% in electric field 1 3 days after HCS

G. B. Burns; B. A. Tinsley; A. R. Klekociuk; O. A. Troshichev; A. V. Frank-Kamenetsky; M. L. Duldig; E. A. Bering; J. M. Clem

2006-01-01

67

Gravity and Orbits: Orbits  

NSDL National Science Digital Library

This Science Object is the third of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of how gravitational forces influence the motion of an object in orbit. When a force acts toward a single center, an object's forward motion and its motion toward that center can combine to create a curved path around the center. Gravity governs the motion of all objects in the solar system. The Sun's gravitational pull holds the Earth and other planets in their orbits, just as the planets' gravitational pull keeps their moons in orbit around them. Learning Outcomes:� Describe the conditions that would lead an object into orbital motion in terms of the effects of gravitational force.� Explain how an object orbits a planet in terms of trajectories and free fall.� Identify gravity as the force that keeps the planets in their orbits around the Sun and the moons in their orbits around the planets.

National Science Teachers Association (NSTA)

2006-11-01

68

Galactic cosmic-ray intensity to a heliocentric distance of 18 AU  

SciTech Connect

An updated report is given of observations of galactic cosmic-ray intensity to heliocentric radial distance of 8.6 and 18.4 AU with Pioneer 11 and Pioneer 10, respectively. Solar activity via the magnetic structure of the interplanetary medium continues to modulate the intensity out to the greatest distance reached thus far. During the 7 year period 1972 March to 1979 March, the galactic cosmic-ray intensity E/sub p/>80 MeV as measured by detectors on Pioneers 10 and 11 exhibited aperiodic temporal variations by about a factor of 2 and on a time scale of the order of a year and quasi-persistent cyclic variations of 26 day period and amplitude a few percent. The former are attributed to overall changes in the magnetic field structure of the heliosphere, the latter to fast-slow solar wind streams in and near the ecliptic plane and not to toward-away magnetic field sectors. The apparent heliographic latitude dependence of intensity is 0( +- 1.5)% per 10/sup 0/ in the latitude range +7/sup 0/.7 to +15./sup 0/8, though it is possible that radially dependent temporal variations over the large difference in the heliocentric radial distances of the two spacecraft may make this result of limited significance. For protons of energy E/sub p/>80 MeV, there is a fairly consistent heliocentric radial gradient of +2.1( +- 0.3)% per AU integral intensity until 1978 April--May, at which time a substantial disruption of the distribution of cosmic rays in the heliosphere occurred.

Van Allen, J.A.

1980-06-01

69

Science-philosophy relation and the prevalence of the heliocentric theory.  

NASA Astrophysics Data System (ADS)

The relation between philosophy and science has passed from many phases in history and still is an interesting topic. The value of falsifiability (or refutability) in science was stressed by Popper. Here, as a paradigm, the juxtaposition of the Earth-centered view of the universe and the prevalence of the heliocentric theory is examined. A new physics appeared in the West in the 17th century, under the Cartesian philosophical canopy, the spirit of which had its deep influence on the savants of that period. This new physics, as defined by Galileo and Kepler, was not searching for purpose, but it was seeking for causes.

Theodossiou, E.; Manimanis, V. N.; Danezis, E.

70

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals website is a distribution point for the orbital image generating program "Orbital Viewer" as well as the home of a collection of images generated with the program. Atomic and molecular orbitals are constructed. For atoms, the hydrogenic solution, up to n=30, is generated and for molecules the linear combination of atomic orbitals method is used.

Manthey, David

2009-03-24

71

Optical observations of comet Hale-Bopp (C/1995 O1) at large heliocentric distances before perihelion.  

PubMed

The activity of comet Hale-Bopp (C/1995 O1) was monitored monthly by optical imaging and long-slit spectroscopy of its dust and gas distribution over heliocentric distances of 4.6 to 2.9 astronomical units. The observed band intensities of the NH2 radical and the H2O+ ion cannot be explained by existing models of fluorescence excitation, warranting a reexamination of the corresponding production rates, at least at large heliocentric distances. Comparing the production rate of the CN radical to its proposed parent, HCN, shows no evidence for the need of a major additional source for CN in Hale-Bopp at large heliocentric distances. The dust and CN production rates are consistent with a significant amount of sublimation occurring from icy dust grains surrounding Hale-Bopp. PMID:9072962

Rauer, H; Arpigny, C; Boehnhardt, H; Colas, F; Crovisier, J; Jorda, L; Küppers, M; Manfroid, J; Rembor, K; Thomas, N

1997-03-28

72

The spectrum and spatial distribution of cyanogen in comet Hale-Bopp (C/1995 O1) at large heliocentric distance.  

PubMed

Optical spectra of comet Hale-Bopp (C/1995 O1) at a heliocentric distance of 6.45 astronomical units showed emission from cyanogen gas. The spatial distribution of cyanogen was considerably more diffuse and extended compared to the spatial profile of the dust or grains which were sharply peaked near the center. This behavior is consistent with comets at smaller heliocentric distances suggesting the same or a similar formation mechanism. A cyanogen gas production rate of (1.2 +/- 0.3) x10(26) molecules per second was derived. A model band profile derived from fluorescence equilibrium calculations for the comet's heliocentric velocity and distance agrees with the observed band profile. PMID:9072965

Wagner, R M; Schleicher, D G

1997-03-28

73

The effects of outgassing jets on the rotation of a comet nucleus and on the trajectory of an orbiting spacecraft  

Microsoft Academic Search

An outgassing jet model is presented in this thesis in support of spacecraft navigation for future missions to comets. The outgassing jet is modelled as an emission cone while the comet nucleus is modelled as a uniform density triaxial ellipsoid. The heliocentric orbit motion as well as in the strength of the outgassing jet are accounted for in the equations

Sharyl M. Byram

2009-01-01

74

Feasibility Study of an Ion-Propelled MARS Orbiter/Lander Spacecraft with Solar Photovoltaic Power. Volume I. Summary.  

National Technical Information Service (NTIS)

Volume I describes a solar-electric propelled spacecraft using ion engines and photovoltaic power to effect the heliocentric transfer from Earth to Mars, carrying a lander and orbiter to perform a Voyager-type mission. The mission feasibility is described...

R. S. H. Toms R. L. Waddell S. B. Fine

1966-01-01

75

Meteors in the IAU Meteor Data Center on Hyperbolic Orbits  

NASA Astrophysics Data System (ADS)

The hyperbolic meteor orbits among the 4,581 photographic and 62,906 radar meteors of the IAU MDC have been analysed using statistical methods. It was shown that the vast majority of hyperbolic orbits has been caused by the dispersion of determined velocities. The large proportion of hyperbolic orbits among the known meteor showers strongly suggests the hyperbolicity of the meteors is not real. The number of apparent hyperbolic orbits increases inversely proportional to the difference between the mean heliocentric velocity of meteor shower and the parabolic velocity limit. The number of hyperbolic meteors in the investigated catalogues does not, in any case, represent the number of interstellar meteors in observational data. The apparent hyperbolicity of these orbits is caused by a high spread in velocity determination, shifting a part of the data through the parabolic limit.

Hajduková, M.

2008-06-01

76

Testing relativity and gravitational theories by radar ranging to a heliocentric satellite  

Microsoft Academic Search

By determining to a high degree of accuracy the orbits of particles or photons in the vicinity of the sun information could be obtained which would help distinguish between different theories of gravitation. It is proposed that radar ranging measurements of particle orbits be obtained from a satellite placed in an orbit that passes close to the sun. Thermal problems,

I. W. Roxburgh

1977-01-01

77

Dynamics of transitional region of the solar wind turbulence with heliocentric distance  

NASA Astrophysics Data System (ADS)

Scale-separation model of wave-particle interaction in divergent solar wind was applied to study the transitional region of solar wind turbulence [1]. We concentrated on area from around the end of the inertial range to the region where proton cyclotron dumping is important. Our goal is to investigate how the transitional region changes due to change of the solar wind plasma parameters (and most important due to the change of local cyclotron frequency) with heliocentric distance. Previously we discovered that shell distribution developed in solar wind due to wave-particle interaction is becoming unstable as solar wind expands [2]. Waves that are generated by this instability modify the transitional region of turbulence. [1] Galinsky, V.L and V. I. Shevchenko, Phys. Rev. Letters, 85, 90, 2000. [2] Shevchenko V.I. et al., Phys. of Plasmas, 11, 4290, 2004.

Galinsky, V.; Shevchenko, V. I.

2010-12-01

78

Dynamics of transitional region of the solar wind turbulence with heliocentric distance  

NASA Astrophysics Data System (ADS)

Scale-separation model of wave-particle interaction in divergent solar wind was applied to study the transitional region of solar wind turbulence.ootnotetextGalinsky, V.L and V. I. Shevchenko, Phys. Rev. Letters, 85, 90 (2000). We concentrated on area from around the end of the inertial range to the region where proton cyclotron dumping is important. Our goal is to investigate how the transitional region changes due to change of the solar wind and plasma parameters (and most important due to the change of local cyclotron frequency) with heliocentric distance. Previously we discovered that shell distribution developed in solar wind due to wave-particle interaction is becoming unstable as solar wind expands.ootnotetextShevchenko et al., Phys. of Plasmas,11, 4290 (2004). Waves that are generated by this instability modify the transitional region of turbulence.

Galinsky, V.; Shevchenko, V.

2010-11-01

79

The heliocentric evolution of cometary infrared spectra - Results from an organic grain model  

SciTech Connect

An emission feature peaking near 3.4 microns that is typical of C-H stretching in hydrocarbons and which fits a simple, two-component thermal emission model for dust in the cometary coma, has been noted in observations of Comets Halley and Wilson. A noteworthy consequence of this modeling is that, at about 1 AU, emission features at wavelengths longer than 3.4 microns come to be diluted by continuum emission. A quantitative development of the model shows it to agree with observational data for Comet Halley for certain, plausible values of the optical constants; the observed heliocentric evolution of the 3.4-micron feature thereby furnishes information on the composition of the comet's organic grains. 65 refs.

Chyba, C.F.; Sagan, C.; Mumma, M.J. (Cornell Univ., Ithaca, NY (USA); NASA, Goddard Space Flight Center, Greenbelt, MD (USA))

1989-06-01

80

The possible formation of a hydrogen coma around comets at large heliocentric distances.  

PubMed

An observational test--the detection of a hydrogen coma around comets at large heliocentric distances--is proposed for determining whether comets were formed by the agglomeration of unaltered, ice-coated, interstellar grains. Laboratory experiments showed that amorphous water ice traps H2, D2, and Ne below 20 K and does not release them completely until the ice is heated to 150 K. Gas/ice ratios as high as 0.63 are obtainable. Thus, if the ice-coated interstellar grains were not heated above approximately 110 K, prior to their agglomeration into cometary nuclei, the inward propagating heat waves should release from the comets a continuous flux of molecular hydrogen. This flux would exceed that of water molecules at approximately 3 AU preperihelion and approximately 4 AU postperihelion. PMID:11538469

Bar-Nun, A; Prialnik, D

1988-01-01

81

Possible formation of a hydrogen coma around comets at large heliocentric distances  

SciTech Connect

An observational test, the detection of a hydrogen coma around comets at large heliocentric distances, is proposed for determining whether comets were formed by the agglomeration of unaltered, ice-coated, interstellar grains. Laboratory experiments showed that amorphous water ice traps H/sub 2/, D/sub 2/, and Ne below 20 K and does not release them completely until the ice is heated to 150 K. Gas/ice ratios as high as 0.63 are obtainable. Thus, if the ice-coated interstellar grains were not heated above about 110 K prior to their agglomeration into cometary nuclei, the inward propagating heat waves should release from the comets a continuous flux of molecular hydrogen. This flux would exceed that of water molecules at about 3 AU preperihelion and about 4 AU postperihelion. 15 references.

Bar-Nun, A.; Prialnik, D.

1988-01-01

82

The amplitudes of interplanetary fluctuations: Stream structure, heliocentric distance, and frequency dependence  

SciTech Connect

The authors present a study of the heliocentric distance, frequency, and stream structure dependence of the amplitudes of interplanetary fluctuations in the velocity and magnetic field from 0.3 to nearly 20 AU and for spacecraft-frame periods of 10 days to a few hours. The results constrain theories of the acceleration of the solar wind and of the evolution of fluctuation amplitudes. They show that the magnetic fluctuation amplitude normalized by the strength of the magnetic field is largely independent of stream structure at the scales studied. Using this fact, they find that the WKB prediction generally provides a good approximation to the magnetic amplitude evolution for all but the smallest scales in the inner heliosphere, which show a dissipation with respect to the WKB prediction, and the largest scales in the outer heliosphere, which decrease more slowly than the simple theory predicts. Velocity fluctuations are shown to generally follow the level of the magnetic fluctuations at the higher frequencies of this study, although it is the energy densities of the velocity and magnetic fluctuations that correlate well rather than the velocity and magnetic fluctuations themselves. Near 0.3 AU the energy in the largest scale velocity fluctuations is, on average, a few times larger than that in the magnetic fluctuations, but with increasing heliocentric distance the magnetic fluctuations become slightly dominant on all scales. The dominance of the kinetic energy in the inner heliosphere is limited to the radial component of the velocity while the transverse components exhibit a more wave-like near equipartition between kinetic and magnetic energy.

Roberts, D.A.; Goldstein, M.L. (NASA Goddard Space Flight Center, Greenbelt, MD (United States)); Klein, L.W. (Applied Research Corp., Landover, MD (United States))

1990-04-01

83

Fundamental and Harmonic Emission in Type III Solar Radio Bursts – III. Heliocentric Variation of Interplanetary Beam and Source Parameters  

Microsoft Academic Search

The parameters of type III solar radio sources have been observed to vary approximately as powers of the heliocentric distance. Recent theoretical studies of fundamental and harmonic emission are used to express the power-law exponents in terms of five basic ones. The results are then used to obtain a best fit to these five exponents, consistent with observed values of

P. A. Robinson; I. H. Cairns

1998-01-01

84

Cosmic-ray exposure age and heliocentric distance of the parent bodies of enstatite chondrites ALH 85119 and MAC 88136  

Microsoft Academic Search

We measured concentrations and isotopic ratios of noble gases in enstatite (E) chondrites Allan Hills (ALH) 85119 and MacAlpine Hills (MAC) 88136. These two meteorites contain solar and cosmogenic noble gases. Based on the solar and cosmogenic noble gas compositions, we calculated heliocentric distances, parent body exposure ages, and space exposure ages of the two meteorites. The parent body exposure

D. Nakashima; T. Nakamura; R. Okazaki

2006-01-01

85

Domain analysis and information retrieval through the construction of heliocentric maps based on ISI-JCR category cocitation  

Microsoft Academic Search

We propose the use of ISI-JCR categories as units of cocitation and measurement for the construction of heliocentric maps. The use of a spatial metaphor allows us to illustrate, analyze and compare domains in terms of the categories and their interconnections or links. We can also move around within the structure of these domains for further analysis, and access the

Felix de Moya-Anegon; Benjamin Vargas-Quesada; Zaida Chinchilla-Rodriguez; Elena Corera-Alvarez; Victor Herrero-Solana; Francisco J. Munoz-Fernandez

86

Characteristics of large Forbush-type decreases in the cosmic radiation 2. Observations at different heliocentric radial distances  

Microsoft Academic Search

Cosmic ray data from IMP 8, Voyager 1 and 2, Pioneer 10 are used to investigate the heliocentric radial dependence of the characteristics of about 20 Forbush-type transient decreases which occurred from 1978 to 1984. These characteristics include (1) the recovery time, (2) the amplitude, and (3) the time to decrease to minimum. It is found that the average recovery

W. R. Webber; J. A. Lockwood; J. R. Jokipii

1986-01-01

87

Telemetry Coding Study for the International Magnetosphere Explorers, Mother/Daughter and Heliocentric Missions. Volume 2: Final Report.  

National Technical Information Service (NTIS)

A convolutional coding theory is given for the IME and the Heliocentric spacecraft. The amount of coding gain needed by the mission is determined. Recommendations are given for an encoder/decoder system to provide the gain along with an evaluation of the ...

D. E. Cartier

1973-01-01

88

A Synoptic Analysis of the Change from the Geocentric to the Heliocentric Conception of the Solar System.  

ERIC Educational Resources Information Center

|The changes which occurred in man's view of the solar system from the time of Ptolemy to that of Galileo are presented. Contained is a brief review of the chain of events which resulted in the acceptance of a heliocentric system. Ptolomy's theory is described and a diagram illustrates the paths of the epicycle of Mars according to his geocentric…

Wilson, Roosevelt L.

89

Nuclear-electric reusable orbital transfer vehicle  

NASA Astrophysics Data System (ADS)

To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined that utilize electric propulsion supported by the nuclear reactor's power for multiple transfers of cargo between low earth orbit (LEO) and geosynchronous earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the orbital transfer vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925-km altitude, 28.5-deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an orbital maneuvering vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO for transfer by OMV to the Shuttle. OTV propellant is resupplied, and the ion thrusters are replaced, by the OMV before each sortie to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to earth. The nominal cargo capability to GEO is 6000 kg, with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo or by changing to mercury propellant.

Jaffe, Leonard D.

1988-10-01

90

The heliocentric evolution of cometary infrared spectra: results from an organic grain model.  

PubMed

Observations of Comets Halley and Wilson reveal an emission feature peaking near 3.4 micrometers, characteristic of C-H stretching in hydrocarbons. We have previously (Chyba and Sagan 1987a, Nature (London) 330, 350-353) fit this feature with a simple two-component thermal emission model for dust in the cometary coma (one component corresponding to large, cool, optically thick particles, the other due to smaller, hotter, organic grains) by employing laboratory spectra of the organic residue produced by the irradiation of carbon-bearing ices. This procedure yields optical depths in agreement with limits from spacecraft data. One remarkable result of such modeling is that at approximately 1 AU emission features at wavelengths longer than 3.4 micrometers are largely overwhelmed (or "diluted") by continuum emission. The large particle optical depth is approximately 10(2) times that of the emitting organics, so that, relative to the continuum, only near the continuum minimum can the emitting organics make a significant contribution. At approximately 1 AU, the 3.4-micrometers feature is the sole feature near that minimum, lying at the intersection of the curves for particle thermal emission and scattered sunlight. Thus, since as a comet moves away from perihelion the intersection of the scattered solar spectrum and the comet's thermal emission spectrum will move to longer wavelengths, we predicted (Chyba and Sagan 1987a) that the 3.4-micrometers feature is diluted while those at longer wavelengths are progressively revealed--so long as the comet retains its coma. We now quantitatively develop this model and find agreement with observational data for Comet Halley for certain plausible values of optical constants. Thus the observed heliocentric evolution of the 3.4-micrometers feature provides information on the composition, and perhaps structure, of the organic grains in Comet Halley. In addition, we argue that the heliocentric evolution of organic features will differ in the cases of thermal emission from small grains and gas-phase fluorescence. Therefore observations of cometary spectral evolution can in principle distinguish between solid or gas-phase origins for these features. PMID:11542163

Chyba, C F; Sagan, C; Mumma, M J

1989-01-01

91

Comet Odyssey: Comet Nucleus Orbiter  

NASA Astrophysics Data System (ADS)

Comet Odyssey is a comet nucleus orbiter mission, proposed to NASA's Discovery program in 2004. The goal of the mission is to completely characterize a cometary nucleus, both physically and compositionally, as can only be done during an extended rendezvous and not with a fast flyby. Comet Odyssey will launch in October 2009 on a Delta II 7925 and use a solar-electric powered spacecraft to effect a rendezvous with periodic comet 46P/Wirtanen in October 2013. Arrival is 96 days after perihelion at a heliocentric distance of 1.61 AU. Comet Odyssey's science payload includes narrow- and wide-angle CCD cameras, an infrared thermal imager, a gas chromatograph/mass spectrometer, an XRD/XRF dust compositional analyzer, and a dust counter and accumulation sensors. The Comet Odyssey spacecraft implementation uses a high heritage approach of flight proven and redundant hardware. The 3-engine ion propulsion subsystem is derived from that on Dawn but includes the capability for multi-engine thrusting. Comet Odyssey will approach the Wirtanen nucleus and make repeated slow flybys through the active cometary coma for a period of three months. It will then be placed in a ˜100-km radius orbit around the nucleus, with a plan to eventually orbit at 40-km altitude or less. From that altitude the narrow-angle camera will map the entire nucleus surface at 1 meter/pixel and the thermal imager will map at 19 meter/pixel. The orbital portion of the nominal mission will last 4.5 months, following the comet outward from the Sun to 3.3 AU as the comet evolves from an active to a quiescent state. En route to P/Wirtanen, the Comet Odyssey spacecraft will perform a close flyby of the 200-km diameter, G-type, main belt asteroid 19 Fortuna in January 2012 and make appropriate remote sensing observations.

Weissman, P. R.; Smythe, W. D.; Spitz, S. J.; Bernard, D. E.; Bailey, R. W.

2004-11-01

92

Numerical investigation of planetesimal collision trajectories with a Moon accumulating in Earth orbit  

SciTech Connect

In the scenario of lunar origin in which the Moon is assumed to have accreted most of its mass while in orbit about the Earth, planetasimals on the accretion knowledge of the relative impact rates of heliocentric planetting Earth and Moon is essential for any attempt to establish dynamical constraints on lunar origin. Numerical integrations of the regularized equations of motion for four bodies (Sun, Earth, Moon, planetismal) were done. A planetismal impact trajectory was calculated by assuming that the planetismal has hit the surface of the Moon at an assumed location, traveling in an assumed direction, and with an assumed impact speed. Next, the equations of motion were numerically integrated backward in time in order to determine from where the planetismal has come. In this way those volumes in heliocentric orbital element space which contribute trajectories that directly impact the Moon.

Cox, L.P.

1984-01-01

93

Substantial outgassing of CO from comet Hale-Bopp at large heliocentric distance.  

PubMed

When comet C/1995 O1 (Hale-Boop) was discovered, at a distance of seven astronomical units from the sun, it was more than one hundred times brighter than comet Halley at the same distance. A comet's brightness is derived from the reflection of sunlight from dust grains driven away from the nucleus by the sublimation of volatile ices. Near the sun, sublimation of water ice (a main constituent of comet nuclei) is the source of cometary activity; but at its current heliocentric distance, Hale-Boop is too cold for this process to operate. Other comets have shown activity at large distances, and in the case of comet Schwassmann-Wachmann 1, carbon monoxide has been detected in quantities sufficient to generate its observed coma. Here we report the detection of CO emission from Hale-Boop, at levels indicating a very large rate of outgassing. Several other volatile species were searched for, but not detected. Sublimation of CO therefore appears to be responsible for the present activity of this comet, and we anticipate that future observations will reveal the onset of sublimation of other volatile species as the comet continues its present journey towards the sun. PMID:8600385

Biver, N; Rauer, H; Despois, D; Moreno, R; Paubert, G; Bockelée-Morvan, D; Colom, P; Crovisier, J; Gérard, E; Jorda, L

1996-03-14

94

Evolution of Coronal Mass Ejection Morphology with Increasing Heliocentric Distance. II. In Situ Observations  

NASA Astrophysics Data System (ADS)

Interplanetary coronal mass ejections (ICMEs) are often observed to travel much faster than the ambient solar wind. If the relative speed between the two exceeds the fast magnetosonic velocity, then a shock wave will form. The Mach number and the shock standoff distance ahead of the ICME leading edge is measured to infer the vertical size of an ICME in a direction that is perpendicular to the solar wind flow. We analyze the shock standoff distance for 45 events varying between 0.5 AU and 5.5 AU in order to infer their physical dimensions. We find that the average ratio of the inferred vertical size to measured radial width, referred to as the aspect ratio, of an ICME is 2.8 ± 0.5. We also compare these results to the geometrical predictions from Paper I that forecast an aspect ratio between 3 and 6. The geometrical solution varies with heliocentric distance and appears to provide a theoretical maximum for the aspect ratio of ICMEs. The minimum aspect ratio appears to remain constant at 1 (i.e., a circular cross section) for all distances. These results suggest that possible distortions to the leading edge of ICMEs are frequent. But, these results may also indicate that the constants calculated in the empirical relationship correlating the different shock front need to be modified; or perhaps both distortions and a change in the empirical formulae are required.

Savani, N. P.; Owens, M. J.; Rouillard, A. P.; Forsyth, R. J.; Kusano, K.; Shiota, D.; Kataoka, R.; Jian, L.; Bothmer, V.

2011-05-01

95

Low cost transfer into useful sun-synchronous orbits at Mars  

NASA Astrophysics Data System (ADS)

Mars oblateness has been found to provide sun-synchronous orbits, including orbits with stationary apsides, similar to those used at earth. A low mass and low data rate complement of scientific instruments placed in such orbits can provide exciting planetary investigations such as the Mars Orbiter Water Mission described herein. Use of a modest Shuttle kickstage (PAM-A) and existing spacecraft hardware makes this mission low-cost. A preliminary mission and spacecraft design is described. The major emphasis of the paper is on the mechanics of heliocentric transfer for the 1986 and 1988 launch opportunities, Martian sun-synchronous orbit geometries, injectable mass capabilities, and methods of achieving these scientifically useful orbits.

Glickman, R. E.; Stuart, J. R.

1981-08-01

96

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals Web site "was established as part of an (ongoing) project at Purdue University to develop 'visualization modules' for general chemistry students." Using the Chime plug-in, which allows unique and stunning visualizations, visitors can learn what an atomic orbital is; what the 1s, 2s, 3s, 2p, 3p, and 3d orbitals are; what hybrid orbitals are; and more. The combination of easy-to-read descriptions and educational graphics make the site a great learning resource for high school and even college level chemistry students.

2007-06-05

97

Heliocentric evolution of the degradation of polyoxymethylene: Application to the origin of the formaldehyde (H 2CO) extended source in Comet C\\/1995 O1 (Hale–Bopp)  

Microsoft Academic Search

The H2CO production rates measured in Comet C\\/1995 O1 (Hale–Bopp) from radio wavelength observations [Biver, N., and 22 colleagues, 2002a. Earth Moon Planets 90, 5–14] showed a steep increase with decreasing heliocentric distance. We studied the heliocentric evolution of the degradation of polyoxymethylene (formaldehyde polymers: (CH2O)n, also called POM) into gaseous H2CO. POM decomposition can indeed explain the H2CO density

Nicolas Fray; Yves Bénilan; Nicolas Biver; Dominique Bockelée-Morvan; Hervé Cottin; Jacques Crovisier; Marie-Claire Gazeau

2006-01-01

98

Achieving Better Than 1 Minute Accuracy in the Heliocentric and Barycentric Julian Dates  

NASA Astrophysics Data System (ADS)

As the quality and quantity of astrophysical data continue to improve, the precision with which certain astrophysical events can be timed becomes limited not by the data themselves, but by the manner, standard, and uniformity with which time itself is referenced. While some areas of astronomy (most notably pulsar studies) have required absolute time stamps with precisions of considerably better than 1 minute for many decades, recently new areas have crossed into this regime. In particular, in the exoplanet community, we have found that the (typically unspecified) time standards adopted by various groups can differ by as much as a minute. Left uncorrected, this ambiguity may be mistaken for transit timing variations and bias eccentricity measurements. We argue that, since the commonly-used Julian Date, as well as its heliocentric and barycentric counterparts, can be specified in several time standards, it is imperative that their time standards always be reported when accuracies of 1 minute are required. We summarize the rationale behind our recommendation to quote the site arrival time, in addition to using BJD, the Barycentric Julian Date in the Barycentric Dynamical Time standard for any astrophysical event. The BJD is the most practical absolute time stamp for extraterrestrial phenomena, and is ultimately limited by the properties of the target system. We compile a general summary of factors that must be considered in order to achieve timing precisions ranging from 15 minutes to 1 ?s. Finally, we provide software tools that, in principal, allow one to calculate BJD to a precision of 1 ?s for any target from anywhere on Earth or from any spacecraft.

Eastman, Jason; Siverd, Robert; Gaudi, B. Scott

2010-08-01

99

Physical properties and orbital stability of the Trojan asteroids  

NASA Astrophysics Data System (ADS)

All the Trojan asteroids orbit about the Sun at roughly the same heliocentric distance as Jupiter. Differences in the observed visible reflection spectra range from neutral to red, with no ultra-red objects found so far. Given that the Trojan asteroids are collisionally evolved, a certain degree of variability is expected. Additionally, cosmic radiation and sublimation are important factors in modifying icy surfaces even at those large heliocentric distances. We search for correlations between physical and dynamical properties, we explore relationships between the following four quantities; the normalised visible reflectivity indexes ( S), the absolute magnitudes, the observed albedos and the orbital stability of the Trojans. We present here visible spectroscopic spectra of 25 Trojans. This new data increase by a factor of about 5 the size of the sample of visible spectra of Jupiter Trojans on unstable orbits. The observations were carried out at the ESO-NTT telescope (3.5 m) at La Silla, Chile, the ING-WHT (4.2 m) and NOT (2.5 m) at Roque de los Muchachos observatory, La Palma, Spain. We have found a correlation between the size distribution and the orbital stability. The absolute-magnitude distribution of the Trojans in stable orbits is found to be bimodal, while the one of the unstable orbits is unimodal, with a slope similar to that of the small stable Trojans. This supports the hypothesis that the unstable objects are mainly byproducts of physical collisions. The values of S of both the stable and the unstable Trojans are uniformly distributed over a wide range, from 0%/1000 Å to about 15%/1000 Å. The values for the stable Trojans tend to be slightly redder than the unstable ones, but no significant statistical difference is found.

Melita, M. D.; Licandro, J.; Jones, D. C.; Williams, I. P.

2008-06-01

100

Study of the Forbidden Oxygen Lines in Comets at Different Heliocentric and Nucleocentric Distances  

NASA Astrophysics Data System (ADS)

Oxygen is an important element in the chemistry of the solar system objects given its abundance and its presence in many molecules including H2O 80% of cometary ices). The analysis of oxygen atoms in comets can provide information not only on the comets themselves but also on the solar system. These atoms have been analyzed using the 3 forbidden oxygen lines [OI] observed in emission in the optical region at 5577.339 Å (the green line), 6300.304 Å and 6363.776 Å (the red lines) (Swings, 1962). Our analysis is based on a sample of 12 comets of various origins. The observing material is made of 53 high signal-to-noise spectra obtained with the high-resolution UVES spectrograph at the ESO VLT from 2002 to 2012 (Manfroid et al, 2009). After noticing that the green line is blended with one C2 line, we built synthetic spectra of C2 for each observing circumstances and we subtracted its contribution to the cometary spectra in order to ensure the decontamination of the 5577 Å line. Then, we measured the intensity of the 3 [OI] lines at different heliocentric distances. By comparing the green to red lines ratio (G/R) with the Bhardwaj & Raghuram (2012) effective excitation rates, we found that H2O is the main parent molecule when the comet is observed at 1 au. When the comet is located beyond 2.5 au from the Sun, CO2 also contributes to the production of oxygen. Studying forbidden oxygen lines could be a new way to estimate the abundances of CO2 in comets, a very difficult task from the ground (Decock et al. 2013). In order to estimate the effect of the quenching on our results, we analyzed the evolution of the G/R ratio at different nucleocentric distances. For nearby comets, we divided the extended 2D spectrum into several zones in order to analyze the oxygen lines as close as possible to the nucleus (down to ~10 km for the closest comets). Their analysis will allow us to study the link of the oxygen lines with the nucleocentric distance. We found a clear variation of the G/R ratio close to the comet nucleus that is in agreement with a contribution from CO2 as predicted by Raghuram & Bhardwaj (2013).

Decock, Alice; Rousselot, P.; Jehin, E.; Hutsemékers, D.; Manfroid, J.; Bhardwaj, A.; Raghuram, S.

2013-10-01

101

Orbital Dynamics  

NSDL National Science Digital Library

This video from SpaceTEC National Aerospace Technical Education Center explains the mechanics of orbital dynamics and Newton's first law of motion. This three minute video is one of the aerospace certification readiness courses.

2011-07-27

102

Space-based Search for Transiting Exoplanets Orbiting Bright Stars  

NASA Astrophysics Data System (ADS)

At the current stage of research transiting planets hold the key to advancing our knowledge of exoplanets as they are the only targets that allow determination of many of the key plane-tary parameters. Because the employed techniques are differential (either photometry or spec-troscopy) and the planet is significantly fainter the host star the dominant limitation is simply the number of photons. This puts a very high premium on transiting planets with bright parent stars. The ExoPlanet Task Force recognized the high value of planets transiting bright stars and identified the need to perform a wide area space-based transit survey. In this presentation I will describe a program that addresses the ExoPTF recommendation by using the output of one of the instruments on the currently operating space mission STEREO. STEREO is the third mission in NASA's Solar Terrestrial Probes program. It uses two nearly identical spacecrafts -one on an Earth-leading orbit and one on an Earth-trailing orbit -each equipped with a suit of five small telescopes to provide a stereoscopic view of the coronal mass ejections (CME) as they propagate away from the Sun. As each of these telescopes observes a portion of the heliospehre, they also image the star field in the background. For the purposes of this study we will consider only the images obtained by the HI-1 instruments. Other instruments, although showing the stellar background as well, do not have the data output suitable for a search for transiting exoplanets. This project described here has the potential of delivering a number of very high value targets for follow-up studies with a wide range of facilities, both ground-based and space-based. It will provide a complete survey of all bright stars (<10m) for 18% of the sky. The photometric data series have the sensitivity to detect all transiting hot-Jupiters and other gas giants with periods up to ˜20 days and even some Neptune size planets orbiting bright and/or late type stars. On the extreme bright end, the survey is sensitive to some super-Earth size planets, but the available number of target stars is small. In my presentation I will describe the capabilities and limitations of the project, will demon-strate the utility of the HI-1 images for searching for transiting exoplanets, and will describe the existing data for several RV discovered planets.

Tsvetanov, Zlatan

103

A simple procedure to extend the Gauss method of determining orbital parameters from three to N points  

NASA Astrophysics Data System (ADS)

A simple procedure is developed to determine orbital elements of an object orbiting in a central force field which contribute more than three independent celestial positions. By manipulation of formal three point Gauss method of orbit determination, an initial set of heliocentric state vectors r i and dot{{r}}i is calculated. Then using the fact that the object follows the path that keep the constants of motion unchanged, I derive conserved quantities by applying simple linear regression method on state vectors r i and dot{{r}}i. The best orbital plane is fixed by applying an iterative procedure which minimize the variation in magnitude of angular momentum of the orbit. Same procedure is used to fix shape and orientation of the orbit in the plane by minimizing variation in total energy and Laplace Runge Lenz vector. The method is tested using simulated data for a hypothetical planet rotating around the sun.

Mirtorabi, Taghi

2013-10-01

104

Nuclear reactor power for an electrically powered orbital transfer vehicle  

SciTech Connect

To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined which utilize electric propulsion and this nuclear reactor power for multiple transfers of cargo between low earth orbit (LEO) and geosynchronous earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the Orbital Transfer Vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925 km altitude, 28.5 deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an Orbital Maneuvering Vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO, for transfer by OMV to the Shuttle. OTV propellant is resupplied and the ion thrusters are replaced by the OMV before each trip to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to earth. The nominal cargo capability to GEO is 6000 kg with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo, or by changing to mercury propellant.

Jaffe, L.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R.; Fujita, T.; Grossman, M.; Kia, T.; Nesmith, B.

1987-05-01

105

Nuclear reactor power for an electrically powered orbital transfer vehicle  

SciTech Connect

To help determine the systems requirements for a 300-kWe space nuclear reactor power system, a mission and spacecraft have been examined which utilize electric propulsion and this nuclear reactor power for multiple transfers of cargo between low Earth orbit (LEO) and geosynchronous Earth orbit (GEO). A propulsion system employing ion thrusters and xenon propellant was selected. Propellant and thrusters are replaced after each sortie to GEO. The mass of the Orbital Transfer Vehicle (OTV), empty and dry, is 11,000 kg; nominal propellant load is 5000 kg. The OTV operates between a circular orbit at 925 km altitude, 28.5 deg inclination, and GEO. Cargo is brought to the OTV by Shuttle and an Orbital Maneuvering Vehicle (OMV); the OTV then takes it to GEO. The OTV can also bring cargo back from GEO, for transfer by OMV to the Shuttle. OTV propellant is resupplied and the ion thrusters are replaced by the OMV before each trip to GEO. At the end of mission life, the OTV's electric propulsion is used to place it in a heliocentric orbit so that the reactor will not return to Earth. The nominal cargo capability to GEO is 6000 kg with a transit time of 120 days; 1350 kg can be transferred in 90 days, and 14,300 kg in 240 days. These capabilities can be considerably increased by using separate Shuttle launches to bring up propellant and cargo, or by changing to mercury propellant.

Jaffe, L.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R.; Fujita, T.; Grossman, M.; Kia, T.; Nesmith, B.

1987-01-01

106

Orbital Elements  

NSDL National Science Digital Library

Coordinates for tracking the International Space Station and the Mir Space Station are available here from NASA's Johnson Space Center Flight Design and Dynamics Division. The Orbital Elements page offers real-time data for use in ground track plotting programs. The site cautions the data are for ground track plotting programs only and "should not be used for precise applications or analysis!"

107

Orbital pseudotumor.  

PubMed

Orbital pseudotumor is a benign condition that accounts for approximately 10% of all orbital mass lesions. Any part of the orbit may be involved. The etiology is unknown. The presentation may be either acute or subacute. Patients may present with a palpable mass, a swollen eyelid, congestion, pain, diminished ocular motility, and/or decreased visual acuity. Approximately, 25% of patients present with bilateral disease. A modest proportion of patients experience resolution of their symptoms without treatment. Biopsy is indicated for those who do not respond to, or relapse after, first-line therapy. Oral corticosteroids are the initial treatment and approximately 80% of patients respond. Roughly half of those who respond to corticosteroids relapse. Second-line therapy consists of either low-dose radiotherapy (20-30 Gy at 2 Gy per fraction), cytotoxic chemotherapy, or immunosuppressive agents. Radiotherapy results in long-term local control rates of 50% or higher. Limited lesions may be successfully resected. A small subset of patients may experience inexorable progression to a fixed, painful, sightless eye and require orbital exenteration. PMID:19738455

Mendenhall, William M; Lessner, Alan M

2010-06-01

108

Nuclear orbiting  

SciTech Connect

Nuclear orbiting following collisions between sd and p shell nuclei is discussed. The dependence of this process on the real and imaginary parts of the nucleus-nucleus potential is discussed, as well as the evolution of the dinucleus toward a fully equilibrated fused system. 26 refs., 15 figs.

Shapira, D.

1988-01-01

109

Elliptical Orbits  

NSDL National Science Digital Library

Although not inquiry, this activity is important for students to understand what an ellipse is and what a focus is, and to break misconceptions about Earth's orbit being highly elliptical. This is the perfect place to check to see if students have the mis

Horton, Michael

2009-05-30

110

Heliocentric radial intensity profiles of galactic cosmic rays measured by the IMP, Voyager, and Pioneer spacecraft in solar 11-year modulation cycles of opposite magnetic polarity  

Microsoft Academic Search

We examine in this paper the heliocentric radial intensity profiles at heliolatitudes <35° of five energies\\/species of galactic cosmic rays as measured by IMP, Pioneer 10, and Voyagers 1 and 2 over several 11-year solar cycles of different solar magnetic polarity. At times of maximum solar modulation the radial profiles in each cycle are remarkably similar. At times of minimum

W. R. Webber; J. A. Lockwood

2004-01-01

111

Forbidden oxygen lines in Comets C/2006 W3 Christensen and C/2007 Q3 Siding Spring at large heliocentric distance: Implications for the sublimation of volatile ices  

NASA Astrophysics Data System (ADS)

We present observations and analysis of the forbidden oxygen lines in Comets C/2006 W3 (Christensen) and C/2007 Q3 (Siding Spring) at heliocentric distances of 3.13 and 2.96 AU, respectively. We obtained the observations using the ARCES echelle spectrometer, which is mounted on the Astrophysical Research Consortium 3.5-m telescope at Apache Point Observatory. We detected the 5577, 6300, and 6364 Å atomic oxygen lines in Christensen and we calculated the ratio of the green (5577 Å) line flux to that of the red doublet (6300 and 6364 Å). We obtained a ratio of 0.24 ± 0.08, a number higher than previous measurements for other comets at smaller heliocentric distance. This shows that CO and/or CO2 made detectable contributions to the O I population in the coma of Christensen. We only detected the 6300 Å line in Siding Spring, resulting in an upper limit for the oxygen line ratio of 0.20. Based on the derived flux for the 6300 Å line, we constrain the CO2 and H2O production rate in Siding Spring. A comparison of our results at ˜3 AU to previous findings for comets at this approximate heliocentric distance suggests that a heliocentric distance of 3 AU is a transition region between H2O and CO2 dominated activity in comets.

McKay, Adam J.; Chanover, Nancy J.; Morgenthaler, Jeffrey P.; Cochran, Anita L.; Harris, Walter M.; Russo, Neil Dello

2012-07-01

112

Öpik-type collision probability for high-inclination orbits  

NASA Astrophysics Data System (ADS)

The classical Öpik theory provides an estimate of the collision probability between two bodies on bound, heliocentric or planetocentric orbits under restrictive assumptions of: (i) constant eccentricity and inclination, and (ii) uniform circulation of the longitude of node and argument of pericenter. These assumptions are violated whenever either of the orbits has a large inclination with respect to the local Laplace plane or large eccentricity, and their motion is perturbed by an exterior (tidal) gravitational field of a planet or the Sun. In this situation, known as the Lidov-Kozai regime, the eccentricity and inclination values exhibit large and correlated oscillations. At the same time, the longitude of node and the argument of pericenter may have strongly nonlinear time evolution, with the latter being even bound to a small interval of values. Here we develop a new Öpik-type collision probability theory which is valid even for highly inclined and/or eccentric orbits of the projectile. We assume that the orbit of the target is circular and in the local Laplace plane. Such a generalized setting is necessary, as an example, to correctly estimate the terrestrial impact fluxes of sporadic micrometeoroids on high-inclination orbits (notably those from the toroidal source and the associated helion and anti-helion arcs).

Vokrouhlický, David; Pokorný, Petr; Nesvorný, David

2012-05-01

113

On-orbit assembly and servicing of future space observatories  

NASA Astrophysics Data System (ADS)

NASA's experience servicing the Hubble Space Telescope, including the installation of optical elements to compensate for a mirror manufacturing error; replacement of failed avionics and worn-out batteries, gyros, thermal insulation and solar arrays; upgrades to the data handling subsystem; installation of far more capable instruments; and retrofitting the NICMOS experiment with a mechanical cryocooler has clearly demonstrated the advantages of on-orbit servicing. This effort has produced a unique astronomical observatory that is orders of magnitude more capable than when it was launched and can be operated for several times its original design life. The in-space operations capabilities that are developed for NASA's Exploration Program will make it possible to assemble and service spacecraft in space and to service them in cis-lunar and L2 orbits. Future space observatories should be designed to utilize these capabilities. This paper discusses the application of the lessons learned from HST and our plans for servicing the Advanced X-ray Astrophysical Observatory with the Orbital Maneuvering Vehicle and the Space Station Freedom Customer Servicing Facility to future space observatories, such as SAFIR and LifeFinder that are designed to operate in heliocentric orbits. It addresses the use of human and robotic in-space capabilities that would be required for on-orbit assembly and servicing for future space observatories, and describes some of our design concepts for these activities.

Lillie, C. F.

2006-07-01

114

Methods for Orbit Optimization for the LISA Gravitational Wave Observatory  

NASA Astrophysics Data System (ADS)

The Laser Interferometer Space Antenna (LISA) mission is a joint ESA-NASA mission for detecting low-frequency gravitational waves in the frequency range from 0.1 mHz to 1 Hz, by using accurate distance measurements with laser interferometry between three spacecraft, which will be launched around 2015 and one year later reach their orbits around the Sun. In order to operate successfully, it is crucial for the constellation of the three spacecraft to have extremely high stability. In this paper, several problems of the orbit optimization of the LISA constellation are discussed by using numerical and analytical methods for satisfying the requirements of accuracy. On the basis of the coorbital restricted problem, analytical expressions of the heliocentric distance and the trailing angle to the Earth of the constellation's barycenter are deduced, with the result that the approximate analytical solution of first order will meet the accuracy requirement of the spacecraft orbit design. It is proved that there is a value of the inclination of the constellation plane that will make the variation of the arm-length a minimum. The principle for selecting the optimum starting elements of orbits at any epoch is proposed. The method and programming principles of finding the optimized orbits are also presented together with examples of the optimization design.

Li, Guangyu; Yi, Zhaohua; Heinzel, Gerhard; Rüdiger, Albrecht; Jennrich, Oliver; Wang, Li; Xia, Yan; Zeng, Fei; Zhao, Haibin

115

Orbit analysis  

SciTech Connect

The past fifteen years have witnessed a remarkable development of methods for analyzing single particle orbit dynamics in accelerators. Unlike their more classic counterparts, which act upon differential equations, these methods proceed by manipulating Poincare maps directly. This attribute makes them well matched for studying accelerators whose physics is most naturally modelled in terms of maps, an observation that has been championed most vigorously by Forest. In the following sections the author sketchs a little background, explains some of the physics underlying these techniques, and discusses the best computing strategy for implementing them in conjunction with modeling accelerators.

Michelotti, L.

1995-01-01

116

Mission Steering Profiles of Outer Planetary Orbiters Using Radioisotope Electric Propulsion  

NASA Astrophysics Data System (ADS)

Radioisotope Electric Propulsion (REP) has the potential to enable small spacecraft to orbit outer planetary targets with trip times comparable to flyby missions. The ability to transition from a flyby to an orbiter mission lies in the availability of continuous low power electric propulsion along the entire trajectory. The electric propulsion system's role is to add and remove energy from the spacecraft's trajectory to bring it in and out of a heliocentric hyperbolic escape trajectory for the outermost target bodies. Energy is added and the trajectory is reshaped to rendezvous with the closer-in target bodies. Sample REP trajectories will be presented for missions ranging for distances from Jupiter orbit to the Pluto-Kuiper Belt.

Fiehler, Douglas; Oleson, Steven

2004-02-01

117

Dynamical behaviour of planetesimals temporarily captured by a planet from heliocentric orbits: basic formulation and the case of low random velocity  

Microsoft Academic Search

Planetesimals encountering with a planet cannot be captured permanently unless energy dissipation is taken into account, but some of them can be temporarily captured in the vicinity of the planet for an extended period of time. Such a process would be important for the origin and dynamical evolution of irregular satellites, short-period comets, and Kuiper-belt binaries. In this paper, we

Kazunori Iwasaki; Keiji Ohtsuki

2007-01-01

118

Capture of comets from the Oort cloud into Halley-type and Jupiter-family orbits  

NASA Astrophysics Data System (ADS)

This paper analyzes the capture of comets into Halley-type and Jupiter-family orbits from the nearparabolic flux of the Oort cloud. Two types of capture into Halley-type orbits are found. The first type is the evolution of near-parabolic orbits into short-period orbits (with heliocentric orbital periods P < 200 years) as a result of close encounters with giant planets. This process is followed by a very slow drift of cometary orbits into the inner part of the Solar System. Only those comets may pass from short-period orbits into Halley-type and Jupiter-family orbits, which move in orbits with perihelion distances q < 13 au. In the second type of capture, the perihelion distances of cometary orbits become rather small (< 1.5 au) during the first stage of dynamic evolution under the action of perturbations from the Galaxy, and then their semimajor axes decrease as a result of diffusion. The capture takes place, on average, in 500 revolutions of the comet about the Sun, whereas in the first case, the comet is captured, on average, after 12500 revolutions. The region of initial orbital perihelion distances q > 4 au is found to be at least as important a source of Halley-type comets as the region of perihelion distances q < 4 au. More than half of the Halley-type comets are captured from the nearly parabolic flux with q > 4 au. The analysis of the dynamic evolution of objects moving in short-period orbits shows that the distribution of Centaurs orbits agrees well with the observed distribution corrected for observational selection effects. Hence, the hypothesis associating the origin of Centaurs with the Edgeworth-Kuiper belt and the trans-Neptunian region exclusively should be rejected.

Biryukov, E. E.

2007-06-01

119

Long-term evaluation of three-dimensional heliocentric solar sail trajectories with arbitrary fixed sail setting  

Microsoft Academic Search

The solar radiation effects upon the orbital behaviour of an arbitrarily shaped spacecraft (or a solar sail in particular) in a general fixed orientation with respect to the local coordinate frame are investigated. Through introduction of a quasi-angle in the osculating plane, the motion of the orbital plane becomes uncoupled from the in-plane perturbations. Exact solutions in the form of

J. C. Van Der Ha; V. J. Modi

1979-01-01

120

Characteristics of large Forbush-type decreases in the cosmic radiation 2. Observations at different heliocentric radial distances  

SciTech Connect

Cosmic ray data from IMP 8, Voyager 1 and 2, Pioneer 10 are used to investigate the heliocentric radial dependence of the characteristics of about 20 Forbush-type transient decreases which occurred from 1978 to 1984. These characteristics include (1) the recovery time, (2) the amplitude, and (3) the time to decrease to minimum. It is found that the average recovery time is about 5 times longer at R = 30 AU than at 1 AU. The magnitudes of the transient decreases are observed to decrease about 1.5%/AU on average so that the magnitude of the decrease is half as great at Rapprox.30 AU as at 1 AU. The time for the cosmic ray intensity to decrease to the minimum in the transient decrease is found to be greater at larger distances and is about 5 times longer at R = 30 AU than at 1 AU. The behavior of these effects as a function of radius is obviously related to the evolution of the disturbances causing the transient decreases as they propagate outward. A model of the Forbush-type decrease is proposed to explain the observed radial dependence of the recovery time and time to minimum of the decrease. The implications of these results for understanding the relationship between Forbush-type decreases and the 11-year variation are discussed.

Webber, W.R.; Lockwood, J.A.; Jokipii, J.R.

1986-04-01

121

Ulysses observations of solar energetic particle events at large heliocentric distances close to the ecliptic in 1992 and 2003  

NASA Astrophysics Data System (ADS)

The Ulysses spacecraft, launched in October 1990, observed two solar energetic particle events in the declining phase of solar cycle 22 in 1992. The spacecraft was close to the ecliptic at a heliocentric distance of about 5.2 AU. The Earth-Sun-Spacecraft angle was about 120 degree. 11 years and one solar cycle later, Ulysses was at approximately the same location in the heliosphere, when a solar energetic particle event was detected. We identified for all three particle events possible X-ray flares. In all three cases the time-profile of 38-125 MeV protons measured by KET are similar during the first 70 hours. We determined 1) a delay of 11-12 hours with respect to the X-ray event, and 2) a flat maximum intensity registered 25-30 hours later. This first fact implies particle path length of more than 12 AU. Because of the similarity of these three events the same particle propagation mechanism occurred during different interplanetary conditions. Later in the event the time profiles are modified due to propagating disturbances or additional solar particle injections.

Heber, B.; Struminsky, A.; Kallenrode, M.-B.; Muller-Mellin, R.; Klassen, A.; Kunow, H.

122

ERS Orbit Control.  

National Technical Information Service (NTIS)

The European remote sensing mission orbit control is addressed. For the commissioning phase, the orbit is defined by the following requirements: Sun synchronous, local time of descending node 10:30; three days repeat cycle with 43 orbital revolutions; ove...

M. Rosengren

1991-01-01

123

A STUDY OF THE HELIOCENTRIC DEPENDENCE OF SHOCK STANDOFF DISTANCE AND GEOMETRY USING 2.5D MAGNETOHYDRODYNAMIC SIMULATIONS OF CORONAL MASS EJECTION DRIVEN SHOCKS  

SciTech Connect

We perform four numerical magnetohydrodynamic simulations in 2.5 dimensions (2.5D) of fast coronal mass ejections (CMEs) and their associated shock fronts between 10 Rs and 300 Rs. We investigate the relative change in the shock standoff distance, {Delta}, as a fraction of the CME radial half-width, D {sub OB} (i.e., {Delta}/D {sub OB}). Previous hydrodynamic studies have related the shock standoff distance for Earth's magnetosphere to the density compression ratio (DR; {rho} {sub u}/{rho} {sub d}) measured across the bow shock. The DR coefficient, k {sub dr}, which is the proportionality constant between the relative standoff distance ({Delta}/D {sub OB}) and the compression ratio, was semi-empirically estimated as 1.1. For CMEs, we show that this value varies linearly as a function of heliocentric distance and changes significantly for different radii of curvature of the CME's leading edge. We find that a value of 0.8 {+-} 0.1 is more appropriate for small heliocentric distances (<30 Rs) which corresponds to the spherical geometry of a magnetosphere presented by Seiff. As the CME propagates its cross section becomes more oblate and the k {sub dr} value increases linearly with heliocentric distance, such that k {sub dr} = 1.1 is most appropriate at a heliocentric distance of about 80 Rs. For terrestrial distances (215 Rs) we estimate k {sub dr} = 1.8 {+-} 0.3, which also indicates that the CME cross-sectional structure is generally more oblate than that of Earth's magnetosphere. These alterations to the proportionality coefficients may serve to improve investigations into the estimates of the magnetic field in the corona upstream of a CME as well as the aspect ratio of CMEs as measured in situ.

Savani, N. P. [University Corporation for Atmospheric Research (UCAR), Boulder, CO 80307 (United States); Shiota, D. [Computational Astrophysics Laboratory, Advanced Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Kusano, K. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Vourlidas, A. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Lugaz, N., E-mail: neel.savani02@imperial.ac.uk [Experimental Space Plasma Group, University of New Hampshire, Durham, NH 03824 (United States)

2012-11-10

124

UVCS\\/SOHO Observations of H I Lyman Alpha Line Profiles in Coronal Holes at Heliocentric Heights Above 3.0 R?  

Microsoft Academic Search

The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO) has been used to measure\\u000a spectral line profiles for H I Ly? in the south polar coronal hole at projected heliocentric heights from 3.5 to 6.0 R? during 1998 January 5–11. Observations from 1.5 to 2.5 R? were made for comparison. The H I Ly? profile is the

R. M. Suleiman; J. L. Kohl; A. V. Panasyuk; A. Ciaravella; S. R. Cranmer; L. D. Gardner; R. Frazin; R. Hauck; P. L. Smith; G. Noci

1999-01-01

125

Latitude variation of recurrent MeV-energy proton flux enhancements in the heliocentric radial range 11 t 20 AU and possible correlation with solar coronal hole dynamics  

Microsoft Academic Search

Recurrent low energy (> or approx. =0.5 MeV) proton flux enhancements, reliable indicators of corotating plasma interaction regions in interplanetary space, have been observed on the Voyager 1 and 2 and Pioneer 11 spacecraft in the heliographic latitude range 2°S to 23°N and the heliocentric radial range 11 to 20 AU. After a period of rather high correlation between fluxes

S. P. Christon; E. C. Stone

1985-01-01

126

Viking satellite orbit determination  

Microsoft Academic Search

During the summer of 1976, the two Viking spacecraft, each consisting of an orbiter-lander combination, were inserted into orbit about Mars. The paper describes the experiences of the Viking Satellite Orbit Determination Team in determining Mars centered ephemerides of the orbiters and positions of the landers from the two-way Doppler and range data, and synthesizes the different phases of the

C. E. Hildebrand; E. J. Christensen; D. H. Boggs; G. H. Born; H. Hokikian; J. F. Jordan; W. B. Howard

1977-01-01

127

Concepts of orbital mechanics  

Microsoft Academic Search

Parameters determining an orbit, perturbations acting on a satellite and orbital deviations resulting from them, and a study of the particular types of orbits relevant to the use of artificial earth satellites for finding and developing natural resources are presented. The discussion shows the constraints imposed on teledetective search by certain characteristics of the orbits.

A. Alouges

1974-01-01

128

Working With Orbits  

NSDL National Science Digital Library

This site offers two programs to illustrate how orbits work. The Orbital Elements calculator contains animations to see how the appearance of an orbit depends on the values of the orbital elements which include distance from the Sun, eccentricity, pericenter location and anomaly. This is available in two or three dimensions. The Solar System allows users to watch several planets in our Solar System simultaneously orbit the Sun. An additional object (asteroid or comet) is present and users change the orbital parameters to see what types of orbits are possible for this object.

Hamilton, Douglas

129

Spontaneous subperiosteal orbital hemorrhage.  

PubMed

Abstract Subperiosteal orbital hemorrhage typically results from trauma. Spontaneous subperiosteal orbital hemorrhage (SSOH) is rare and has been reported with sudden elevation of cranial venous pressure, bleeding diathesis, and sinusitis. This article presents a series of 9 patients (11 orbits) with SSOH and review the associated systemic conditions. 10 out of 11 orbits (91%) underwent surgical intervention due to advanced orbital signs or poor vision. PMID:23895577

Elia, Maxwell D; Shield, David; Kazim, Michael; Shinder, Roman; Yoon, Michael; McCulley, Timothy J; Shore, John W; Greene, Daniel; Servat, Juan J; Levin, Flora

2013-07-29

130

Orbital fractures: a review  

PubMed Central

This review of orbital fractures has three goals: 1) to understand the clinically relevant orbital anatomy with regard to periorbital trauma and orbital fractures, 2) to explain how to assess and examine a patient after periorbital trauma, and 3) to understand the medical and surgical management of orbital fractures. The article aims to summarize the evaluation and management of commonly encountered orbital fractures from the ophthalmologic perspective and to provide an overview for all practicing ophthalmologists and ophthalmologists in training.

Joseph, Jeffrey M; Glavas, Ioannis P

2011-01-01

131

ERS orbit control  

Microsoft Academic Search

The European remote sensing mission orbit control is addressed. For the commissioning phase, the orbit is defined by the following requirements: Sun synchronous, local time of descending node 10:30; three days repeat cycle with 43 orbital revolutions; overhead Venice tower (12.508206 deg east, 45.314222 deg north). The launch, maneuvers for the initial acquisition of the operational orbit, orbit maintenance maneuvers,

Mats Rosengren

1991-01-01

132

Orbit-Orbit Interactions in Atomic Spectra  

Microsoft Academic Search

Empirical spectroscopic evidence suggests the existence of an orbit-orbit interaction between electrons, of the form alphal1.l2, and of a magnitude comparable to the spin-orbit interaction. The direct magnetic interaction is of this form, but previous calculations have yielded too small a magnitude. We suggest that the magnetic interaction is uniquely sensitive to the correlation of the interacting electrons, and that

C. W. Ufford; H. B. Callen

1958-01-01

133

Transfer orbit determination accuracy for orbit maneuvers  

NASA Astrophysics Data System (ADS)

This work intends to show the accuracy of the orbital elements determined during transfer orbit as a function of data span, as well as the feasibility of performance maneuvers. The orbit estimator used is a weighted least squares algorithm. The observation vector is composed of angle data (azimuth and elevation) and range data and are from the Astra IC mission. The state vector is either propagated by Brower model or numerical integration (for small eccentricities and inclination). The complete software to determine the orbit has been developed by Hughes Aircraft and been used for all Hughes satellite mission.

Pinheiro, Mery Passos

134

Öpik-type Collision Probability For High-inclination Orbits  

NASA Astrophysics Data System (ADS)

The classical Öpik theory provides an estimate of the collision probability between two bodies on bound, heliocentric or planetocentric orbits under restrictive assumptions of: (i) constant eccentricity and inclination, and (ii) uniform circulation of the longitude of node and argument of pericenter. Here we develop a generalization of this formalism that is valid even for highly inclined and/or eccentric orbits of the projectile. We assume that the orbit of the target is circular and in the local Laplace plane. Such a generalized setting is necessary, as an example, for more precise estimation of terrestrial impact fluxes of sporadic micrometeoroids on high-inclined orbits (notably those from the toroidal source and the associated helion and anti-helion arcs). We perform N-body simulations with artificial populations of particles, where the results show a significant difference between the original and the generalized formalism. The classical Öpik formalism predicts a characteristic timescale at which particles are eliminated different from the simulation results, the new values are in satisfactory accordance with the numerical simulations. Another significant difference are the radiant position of the impactors. For given values of Hamiltonian and z-component angular momentum the classical theory predicts infinite number of radiants due to the evolution of orbital elements e, I and ? during the Kozai-Lidov cycle. However, in the more general case we obtain only 4 (or 8) possible impact configurations with the target. These results may lead to significant differences in estimation or processing of collisions between planets and dust, or asteroid,s and also in estimation of collisions in young planetary systems (e.g. LHB in the Solar System). This work has been supported by the grant SVV-265301

Pokorny, Petr; Vokrouhlicky, D.

2012-10-01

135

Pupils Produce their Own Narratives Inspired by the History of Science: Animation Movies Concerning the Geocentric-Heliocentric Debate  

NASA Astrophysics Data System (ADS)

In this paper, we present the design and application of a teaching scenario appropriate for 12-years-old pupils in the primary school aiming to a better understanding of scientific concepts and scientific methods, linking the development of individual thinking with the development of scientific ideas and facilitating a better understanding of the nature of science. The design of the instructional material supporting this scenario has been based on the study of the history of astronomy and especially on: (a) The various theories concerning the movement of Earth, our solar system and the universe. (b) Key-stories highlighting the evolutionary character of scientific knowledge as well as the cultural interrelations of science and society. The design of the teaching scenario has focused on the participation of pupils in gradually evolving discourses and practices encouraging an appreciation of aspects of the nature of science (e.g. the role of observation and hypothesis, the use of evidence, the creation and modification of models). In this case, pupils are asked to produce their own narratives: animation movies concerning the geocentric-heliocentric debate inspired by the history of science, as the animation technique presents strong expressional potential and currently has many applications in the field of educational multimedia. The research design of this current case study has been based on the SHINE research model, while data coming from pupils' animation movies, questionnaires, interviews, worksheets, story-boards and drawings have been studied and analyzed using the GNOSIS research model. Elaborated data coming from our analysis approach reveal the appearance, transformation and evolution of aspects of nature of science appreciated by pupils and presented in their movies. Data analysis shows that during the application pupils gradually consider more and more the existence of multiple answers in scientific questions, appreciate the effect of culture on the way science functions and the way scientists work as well as the effect of new scientific interpretations that replace the old ones in the light of new evidence. The development of pupils' animation movies carrying aspects of the history of astronomy with a strong focus on the understanding of the nature of science creates a dynamic educational environment that facilitates pupils' introduction to a demanding teaching content (e.g. planet, model, retrograde motion) placing it in context (key-stories from the history of science) and at the same time offers to pupils the opportunity to engage their personal habits, interests and hobbies in the development of their science movies.

Piliouras, Panagiotis; Siakas, Spyros; Seroglou, Fanny

2011-07-01

136

Latitude variation of recurrent MeV-energy proton flux enhancements in the heliocentric radial range 11 t 20 AU and possible correlation with solar coronal hole dynamics  

SciTech Connect

Recurrent low energy (> or approx. =0.5 MeV) proton flux enhancements, reliable indicators of corotating plasma interaction regions in interplanetary space, have been observed on the Voyager 1 and 2 and Pioneer 11 spacecraft in the heliographic latitude range 2/sup 0/S to 23/sup 0/N and the heliocentric radial range 11 to 20 AU. After a period of rather high correlation between fluxes at different latitudes in early 1983, distinct differences develop. The evolution of the fluxes appears to be related to the temporal and latitudinal dynamics of solar coronal holes, suggesting that information about the latitudinal structure of solar wind stream sources propagates to these distances.

Christon, S.P.; Stone, E.C.

1985-02-01

137

In Orbit Infrastructure.  

National Technical Information Service (NTIS)

A systematic approach to space activity by using a standardized automated multipurpose system of transportation and accomodation to, in, and from orbit, called In-Orbit Infrastructure (IOI) is discussed. The IOI needs of commercial space platforms for Ear...

J. Lacaze

1983-01-01

138

Mars Reconnaissance Orbiter  

NSDL National Science Digital Library

This is the mission web site for the Mars Reconnaissance Orbiter, which went into orbit around Mars on March 10, 2006. The site provides links to updates and information about the project. The site features links to Mars Reconnaissance Orbiter images, animations, and datasets. Science operations commence in November, 2006.

Laboratory, Jet P.; Administration, National A.

139

Painless orbital myositis  

PubMed Central

Idiopathic orbital inflammation is the third most common orbital disease, following Graves orbitopathy and lymphoproliferative diseases. We present a 11 year old girl with 15 days history of painless diplopia. There was no history of fluctuation of symptoms, drooping of eye lids or diminished vision. She had near total restricted extra-ocular movements and mild proptosis of the right eye. There was no conjunctival injection, chemosis, or bulb pain. There was no eyelid retraction or lid lag. Rest of the neurological examination was unremarkable.Erythrocyte sedimentation rate was raised with eosinophilia. Antinuclear antibodies were positive. Liver, renal and thyroid functions were normal. Antithyroid, double stranded deoxyribonucleic acid and acetylcholine receptor antibodies were negative. Repetitive nerve stimulation was negative. Magnetic resonance imaging (MRI) of the orbit was typical of orbital myositis. The patient responded to oral steroids. Orbital myositis can present as painless diplopia. MRI of orbit is diagnostic in orbital myositis.

Chakor, Rahul T.; Santhosh, N. S.

2012-01-01

140

Chemguide: Atomic Orbitals  

NSDL National Science Digital Library

This web page explains what atomic orbitals are in a way that makes it appropriate for pre-college introductory chemistry or physics courses. It goes into detail on s and p orbitals, including their shapes and energies, while devoting less discussion to d and f orbitals. The author uses an analogy comparing an atom to a multi-story house -- with the nucleus on the ground floor and then various rooms (orbitals) on the higher floors occupied by the electrons. A full page debunks the misconception that "orbitals" are like "orbits" (common among beginning students). Beyond this foundation, the tutorial explores how electrons fill orbitals (from low-to-high energy). It concludes with a set of questions, with answers provided, for self-gauging understanding. This page is part of Chemguide, an informational website developed by a veteran high school teacher to promote deeper understanding of concepts in introductory and intermediate-level chemistry.

Clark, Jim

2013-02-20

141

Painless orbital myositis.  

PubMed

Idiopathic orbital inflammation is the third most common orbital disease, following Graves orbitopathy and lymphoproliferative diseases. We present a 11 year old girl with 15 days history of painless diplopia. There was no history of fluctuation of symptoms, drooping of eye lids or diminished vision. She had near total restricted extra-ocular movements and mild proptosis of the right eye. There was no conjunctival injection, chemosis, or bulb pain. There was no eyelid retraction or lid lag. Rest of the neurological examination was unremarkable.Erythrocyte sedimentation rate was raised with eosinophilia. Antinuclear antibodies were positive. Liver, renal and thyroid functions were normal. Antithyroid, double stranded deoxyribonucleic acid and acetylcholine receptor antibodies were negative. Repetitive nerve stimulation was negative. Magnetic resonance imaging (MRI) of the orbit was typical of orbital myositis. The patient responded to oral steroids. Orbital myositis can present as painless diplopia. MRI of orbit is diagnostic in orbital myositis. PMID:22919201

Chakor, Rahul T; Santhosh, N S

2012-07-01

142

Lorenz Attractor Periodic Orbits  

NSDL National Science Digital Library

The butterfly-like Lorenz attractor is a simplified model of two-dimensional convective fluid flow and is one of the best known images of chaos. Embedded in this attractor are unstable periodic orbits described by Viswanath and this model computes a number of these orbits. Each periodic orbit is classified by the number of times the trajectory orbits the A and B fixed points before it repeats. Note that because the attractor is chaotic and because of numerical errors and the finite precision of the initial conditions, errors accumulate and the trajectory leaves the vicinity of a periodic orbit after a half dozen cycles. The Lorenz Attractor Periodic Orbits Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_chaos_LorenzAttractor.jar file will run the program if Java is installed.

Christian, Wolfgang

2009-05-20

143

Earth orbiting stations  

Microsoft Academic Search

The earth-orbiting station has evolved through Salyut, Skylab, and the Apollo-Soyuz project. The Shuttle combined with Spacelab will permit low-earth-orbit flights of up to 30 days. Later manned and automated free-flying Spacelabs will extend stay-times to 60 days. Bigger space stations housing 6-12 crewmen for up to six months could be built up from modules carried into orbit. Future space

D. W. Patterson; J. W. Gurr; G. V. Butler

1975-01-01

144

Idiopathic orbital pseudotumour.  

PubMed

Idiopathic orbital pseudotumour (IOP) is a benign inflammatory condition usually confined to the orbit. This may involve single or multiple intraorbital structures. Extraorbital extension can also occur. The imaging appearances often mimic other orbital diseases. Both computed tomography (CT) and magnetic resonance imaging (MRI) are frequently used to investigate orbital diseases, and it is important for radiologists to be aware of the variety of imaging appearances that occur in IOP. We present the imaging appearances in histopathologically confirmed cases of IOP and discuss the clinical features, natural history, and differential diagnosis of this condition. PMID:21546008

Ding, Z X; Lip, G; Chong, V

2011-05-04

145

Saturn Orbiter Mission Study.  

National Technical Information Service (NTIS)

A preliminary analysis of the important aspects of missions orbiting the planet Saturn is provided. Orbital missions to Saturn is given serious consideration for the 1980's, or after flybys by Pioneer 10/G and Mariner Jupiter-Saturn 1977. An attempt is ma...

W. C. Wells R. J. Sullivan

1973-01-01

146

Devising geodetic satellite orbits  

Microsoft Academic Search

In the present paper, an intermediate theory of satellite motion, developed within the framework of the problem of six fixed centers with allowance for the influence of eight zonal harmonics of the geopotential, is applied to the analysis of quasi-geosynchronous and heliosynchronous orbits of geodetic satellites. Expressions for selecting nominal parameters for such orbits are proposed.

E. L. Lukashevich

1979-01-01

147

Tethered Orbital Refueling Study.  

National Technical Information Service (NTIS)

One of the major applications of the space station will be to act as a refueling depot for cryogenic-fueled space-based orbital transfer vehicles (OTV), Earth-storable fueled orbit maneuvering vehicles, and refurbishable satellite spacecraft using hydrazi...

D. A. Fester L. K. Rudolph E. R. Kiefel P. W. Abbott P. Grossrode

1986-01-01

148

Stability of halo orbits.  

PubMed

We predict new populations of trapped nonequatorial ("halo") orbits of charged dust grains about an arbitrary axisymmetric planet. Simple equilibrium and stability conditions are derived, revealing dramatic differences between positively and negatively charged grains in prograde or retrograde orbits. Implications for the Cassini mission to Saturn are discussed. PMID:11019061

Howard, J E; Dullin, H R; Horányi, M

2000-04-10

149

From surface to orbit  

Microsoft Academic Search

Space travel is highly expensive and has significant limitations. Among all space activities the process of travelling from the surface to orbit requires the greatest amount of energy, materials and cost. Basically even today, more than 61 years after the first artificial satellite was set to orbit, these difficulties have been the greatest barriers of the dawn of the real

Andras Bela Olah

2011-01-01

150

Spontaneous orbital haemorrhage.  

PubMed Central

A 57-year-old housewife, with controlled hypertension, presented with acute right proptosis and visual loss with external ophthalmoplegia due to spontaneous orbital haemorrhage. Vision and ocular motility were returned to normal by the rapid surgical evacuation of the blood. Acute orbital haemorrhage is an ocular emergency requiring urgent treatment to prevent the usual previously reported outcome of permanent visual loss. Images

Brooks, A. M.; Finkelstein, E.

1984-01-01

151

Space Shuttle orbiter avionics  

Microsoft Academic Search

The paper concerns the Orbiter's integrated avionic system, which consists of multiple computers with attendant software, multifunction man-machine interfaces, digital communications, and multipurpose instrumentation and data handling capability. The design and verification tasks discussed include hardware and software simulation leading to the flight test phases. Some of the major attributes of the orbiter avionic system include redundancy to support time-critical

L. M. Carrier; R. G. Minor

1977-01-01

152

Orbital trapdoor fractures  

PubMed Central

Orbital trapdoor fractures are commonly encountered in children. Awareness of trapdoor fractures is of particular importance. This is because early recognition and treatment are necessary to prevent permanent motility abnormities. In this article, we will provide a brief overview of orbital fractures. The clinical and radiographic features of trapdoor fractures will then be reviewed, followed by a discussion on their proper management.

Phan, Laura T.; Jordan Piluek, W.; McCulley, Timothy J.

2012-01-01

153

Lunar orbiting and landing missions  

Microsoft Academic Search

Orbits for a lunar orbiting spacecraft and unmanned lunar surface rovers are identified. The orbit to the moon is divided into two phases: one is the lunar transfer phase and the other is the landing phase. For each phase standard orbits are designed, and mission profiles are presented. The minimum weight of the lunar orbiting spacecraft is estimated to be

Tsutomu Iwata; Kazumi Okuda; Yutaka Kaneko

1989-01-01

154

Massive congenital orbital teratoma.  

PubMed

Orbital teratomas are rare embryonic tumors composed of a wide diversity of tissues derived from the three germinal layers. The presenting features include, a healthy newborn with extreme unilateral proptosis; marked stretching of the eyelids over a tense, fluctuating mass, with elongation of the palpebral fissure; enlargement of the bony orbit (two to three times normal size) with subsequent nasal and malar deformities; and transillumination of all or part of the orbital mass. Commonly the eye is normally developed but often vision is not preserved either due to exposure or secondary optic atrophy. The objective in the management of orbital teratoma is to save the eye to encourage orbitofacial development, maintain cosmesis and retain some vision. We report a case of massive congenital orbital teratoma successfully removed by an eyelid-sparing exenteration technique. PMID:16304523

Gnanaraj, Lawrence; Skibell, Bentley C; Coret-Simon, Judith; Halliday, William; Forrest, Christopher; DeAngelis, Dan D

2005-11-01

155

Orbital endoscopic surgery  

PubMed Central

Minimally invasive ?keyhole? surgery performed using endoscopic visualization is increasing in popularity and is being used by almost all surgical subspecialties. Within ophthalmology, however, endoscopic surgery is not commonly performed and there is little literature on the use of the endoscope in orbital surgery. Transorbital use of the endoscope can greatly aid in visualizing orbital roof lesions and minimizing the need for bone removal. The endoscope is also useful during decompression procedures and as a teaching aid to train orbital surgeons. In this article, we review the history of endoscopic orbital surgery and provide an overview of the technique and describe situations where the endoscope can act as a useful adjunct to orbital surgery.

Selva, Dinesh

2008-01-01

156

External Resource: What is orbit?  

NSDL National Science Digital Library

A 5-8 NASA Education reference answering the question, " What is orbit?" Topics include: satellite, ecliptic plane, perigee, apogee, escape velocity, geosynchronous, polar orbits, and low Earth orbit.

1900-01-01

157

Lunar Prospector Orbit Determination Results.  

National Technical Information Service (NTIS)

The orbit support for Lunar Prospector (LP) consists of three main areas: (1) cislunar orbit determination, (2) rapid maneuver assessment using Doppler residuals, and (3) routine mapping orbit determination. The cislunar phase consisted of two trajectory ...

M. Beckman M. Concha

1998-01-01

158

Harmonically excited orbital variations  

SciTech Connect

Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.

Morgan, T.

1985-08-06

159

Removal of orbital debris  

NASA Astrophysics Data System (ADS)

The several methods presently identified for the reduction of orbital debris populations are broadly classifiable as either preventive or remedial, and fall within distinctive operational regimes. For all particles, (1) in the 250-2000-km altitude band, intelligent sweepers may be used; (2) for large objects, in the 80-250-km altitude band, orbital decay renders removal impractical; (3) for the 250-750-km altitude band, deorbit devices should be used; (4) for 750-2500-km altitude, OMV rendezvous for propulsive deorbit package attachment is foreseeable; and beyond 2500 km, (5) propulsive escape from earth orbit is required.

Petro, Andrew J.; Talent, David L.

160

Orbital blood cyst.  

PubMed Central

A blood cyst of the orbit is an unusual cause of proptosis and most likely arises in a pre-existing haemangioma. If the cyst occurs at the apex of the orbit the blood should be aspirated. This is followed by excision of the cyst wall, the dissection being done with the aid of an operating microscope. If there is evidence of intracranial connection of the blood cyst, namely, splayed superior orbital fissure or cerebrospinal fluid leak, then the patient should be treated with an antibiotic to prevent intracranial infection. Images

Sevel, D.; Rosales, A.

1978-01-01

161

Optical lattices: Orbital dance  

NASA Astrophysics Data System (ADS)

Emulating condensed-matter physics with ground-state atoms trapped in optical lattices has come a long way. But excite the atoms into higher orbital states, and a whole new world of exotic states appears.

Lewenstein, Maciej; Liu, W. Vincent

2011-02-01

162

Exploratory Orbit Analysis.  

National Technical Information Service (NTIS)

Unlike the other documents in these proceedings, this paper is neither a scientific nor a technical report. It is, rather, a short personal essay which attempts to describe an Exploratory Orbit Analysis (EOA) environment. Analyzing the behavior of a four ...

L. Michelotti

1989-01-01

163

Electric Propulsion Orbital Platform.  

National Technical Information Service (NTIS)

This paper describes the Electric Propulsion Orbital Platform (EPOP), of which the primary objective is to provide an instrumented platform for testing electric propulsion devices in space. It is anticipated that the first flight, EPOP-1, will take place ...

1993-01-01

164

Imaging in orbital trauma  

PubMed Central

Orbital trauma is one of the most common reasons for ophthalmology specialty consultation in the emergency department setting. We survey the literature from 1990 to present to describe the role of computed tomography (CT), magnetic resonance imaging (MRI) and their associated angiography in some of the most commonly encountered orbital trauma conditions. CT orbit can often detect certain types of foreign bodies, lens dislocation, ruptured globe, choroidal or retinal detachments, or cavernous sinus thrombosis and thus complement a bedside ophthalmic exam that can sometimes be limited in the setting of trauma. CT remains the workhorse for acute orbital trauma owing to its rapidity and ability to delineate bony abnormalities; however MRI remains an important modality in special circumstances such as soft tissue assessment or with organic foreign bodies.

Lin, Ken Y.; Ngai, Philip; Echegoyen, Julio C.; Tao, Jeremiah P.

2012-01-01

165

Molecular orbitals of solids  

SciTech Connect

The molecular orbital contains, in general, a linear combination of orbitals of all equivalent atoms in the molecule, and for its construction one can use the method projection operators or induced representation. In this paper, for the expansion of space group representations obtained on induction of representation of local symmetry groups into a space group, the authors use the Mackey linkage theory and the generalized Frobenius reciprocity theorem. On the basis of the Mackey theory a classification of the chemical interactions in crystals composed of one orbital was obtained. Molecular orbitals for the O/sub h//sup 7/ groups of diamond were obtained, and a symmetric analysis of the zone structure of diamond, silicon, and germanium was performed.

Yarzhemskii, V.G.; Murav'ev, E.N.

1987-11-01

166

Orbit Physlet Problems  

NSDL National Science Digital Library

A Danish Website for Interactive Science Education. Html pages in this directory contain scripts that were written by Morten Brydensholt and coworkers for the Orbit website. This commercial website is in Danish. This site provides English translations of this material.

Christian, Wolfgang; Belloni, Mario

2008-02-19

167

Satellites Orbiting Earth  

NSDL National Science Digital Library

In recent years, there has been a push to better understand how Earth works as a system- how land, oceans, air, and life all interact. Satellites in orbit around Earth are a fast and efficient way of gathering remotely sensed data about the planet as a whole. This animated video shows the orbital paths of the satellites in the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS), a collection of satellites that work together to study Earth on a wide scale.

168

Theory of Orbits  

NASA Astrophysics Data System (ADS)

Theory of Orbits treats celestial mechanics as well as stellar dynamics from the common point of view of orbit theory, making use of concepts and techniques from modern geometric mechanics. It starts with elementary Newtonian mechanics and ends with the dynamics of chaotic motion. The two volumes are meant for students in astronomy and physics alike. Prerequisite is a physicist's knowledge of calculus and differential geometry.

Boccaletti, Dino; Pucacco, Giuseppe

169

The Exoplanet Orbit Database  

NASA Astrophysics Data System (ADS)

We present a database of well-determined orbital parameters of exoplanets, and their host stars' properties. This database comprises spectroscopic orbital elements measured for 427 planets orbiting 363 stars from radial velocity and transit measurements as reported in the literature. We have also compiled fundamental transit parameters, stellar parameters, and the method used for the planets discovery. This Exoplanet Orbit Database includes all planets with robust, well measured orbital parameters reported in peer-reviewed articles. The database is available in a searchable, filterable, and sortable form online through the Exoplanets Data Explorer table, and the data can be plotted and explored through the Exoplanet Data Explorer plotter. We use the Data Explorer to generate publication-ready plots, giving three examples of the signatures of exoplanet migration and dynamical evolution: We illustrate the character of the apparent correlation between mass and period in exoplanet orbits, the different selection biases between radial velocity and transit surveys, and that the multiplanet systems show a distinct semimajor-axis distribution from apparently singleton systems.

Wright, J. T.; Fakhouri, O.; Marcy, G. W.; Han, E.; Feng, Y.; Johnson, John Asher; Howard, A. W.; Fischer, D. A.; Valenti, J. A.; Anderson, J.; Piskunov, N.

2011-04-01

170

Two Body Orbits Model  

NSDL National Science Digital Library

The Two Body Orbits model for teachers shows the motion of two objects (binary star or moon-planet system) interacting via Newton's law of universal gravitation. It is designed to teach physics, Earth science, and environmental science topics by showing the spatial path of objects around their common center of mass (barycenter). An optional 3D view shows the celestial sphere and and the orbital plane (ecliptic). Default units are chosen for Earth obit about our Sun so that the distance unit is one astronomical unit and the time unit is one year.   An important feature of the ready-to-run Two Body Orbits simulation is that it can be customized by teachers to meet various learning objectives. The teacher sets the ratio of the two masses, their initial positions and velocities, and various visualization and scale parameters. Documentation, such as an exercise or lesson, can be added to the simulation by entering a filename into the Customization dialog. Selecting the âstudentâ checkbox creates a ready-to-run package with the new configuration without the Customization dialog. The Two Body Orbits model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run Java archive. Double clicking the ejs_mech_orbits_TwoBodyOrbits.jar file will run the program if Java is installed. EJS is a part of the Open Source Physics Project and is available in the OSP Collection.

Christian, Wolfgang

2012-07-18

171

Comparison of orbit phasing maneuvers  

Microsoft Academic Search

Prussing and Chiu developed a general analysis method for optimizing multiple-impulse, time-fixed rendezvous between circular orbits. Orbit phasing maneuvers, where the maneuvering spacecraft simply changes position within the same orbit, are a subset of these general maneuvers. The present analysis compares the use of simple orbit phasing maneuvers with the optimal maneuvers derived by Prussing and Chiu to determine the

John M. Hanson

1990-01-01

172

ARTEMIS Maneuvers into Lunar Orbit  

NASA Video Gallery

This animation visualizes the maneuvers required to move the ARTEMIS spacecraft from their kidney-shaped paths on each side of the moon to orbiting the moon. It took one and a half years, over 90 orbit maneuvers, many gravitational boosts and surprisingly little fuel to move the two spacecraft. The spacecraft have been through orbits never before attempted and made lovely curlicue leaps from one orbit to the next to reach their destination orbit.

Holly Zell

2011-06-23

173

Arenstorf Orbit JS Model  

NSDL National Science Digital Library

Arenstorf orbits are closed trajectories of the restricted three-body problem. That is, two bodies of masses µ and 1-µ moving in a circular rotation, and a third body of negligible mass moving in the same plane. The computation of these orbits is very sensible to small errors and are a good test for the accuracy of numerical methods for solving Ordinary Differential Equations. This simulation compares the solution of two of these orbits using both a 4th-order fixed step and a 5(4) variable step Runge-Kutta algorithm. The adaptive solver uses an event to find the period of the orbit and stop there. Both the computations of the adaptive solver and the event are done with the step size and the tolerance indicated. The Arenstorf Orbit JS Model was developed using the Easy Java Simulations (Ejs) version 5. It is distributed as a ready-to-run html page and requires only a browser with JavaScript support.

Franciscouembre

2013-08-28

174

GOCE Precise Science Orbits  

NASA Astrophysics Data System (ADS)

GOCE (Gravity field and steady-state Ocean Circulation Explorer), as the first ESA (European Space Agency) Earth Explorer Core Mission, is dedicated for gravity field recovery of unprece-dented accuracy using data from the gradiometer, its primary science instrument. Data from the secondary instrument, the 12-channel dual-frequency GPS (Global Positioning System) receiver, is used for precise orbit determination of the satellite. These orbits are used to accu-rately geolocate the gradiometer observations and to provide complementary information for the long-wavelength part of the gravity field. A precise science orbit (PSO) product is provided by the GOCE High-Level Processing Facility (HPF) with a precision of about 2 cm and a 1-week latency. The reduced-dynamic and kinematic orbit determination strategies for the PSO product are presented together with results of about one year of data. The focus is on the improvement achieved by the use of empirically derived azimuth-and elevation-dependent variations of the phase center of the GOCE GPS antenna. The orbits are validated with satellite laser ranging (SLR) measurements.

Bock, Heike; Jäggi, Adrian; Meyer, Ulrich; Beutler, Gerhard; Heinze, Markus; Hugentobler, Urs

175

Reflection Model as Applied for the Analysis of Enhancements of Solar Cosmic Rays at Different Heliocentric Distances: An Example of the Event Observed in June 1991 onboard GRANAT and ULYSSES Spacecraft  

Microsoft Academic Search

In this paper we consider a large-scale enhancement of the intensity of solar protons (E = 1–20 MeV) observed in June 1991 for 26 days at different points of interplanetary space, onboard ULYSSES (in the time period under consideration it was located at a heliocentric distance of 3 AU, at an angular distance of ~70° to the East of the

E. E. Grigorenko; G. P. Lyubimov

2004-01-01

176

Ballistics and Orbits Model  

NSDL National Science Digital Library

The EJS Ballistics and Orbits model displays ballistic trajectories near the Earth. The model shows the trajectory with respect to the inertial coordinate system and the trajectory as seen from a point of view that is co-rotating with the Earth. You can examine and modify this simulation if you have EJS installed by right-clicking within the plot and selecting âOpen EJS Modelâ from the pop-up menu item. The Ballistics and Orbits model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_nl_teunissen_ballistics_and_orbits.jar file will run the program if Java is installed. Additional information about this model can be found by visiting the authorâs web site: http://www.cleonis.nl/index.htm.

Teunissen, Cleon

2009-11-03

177

Orbit utilization - Current regulations  

NASA Astrophysics Data System (ADS)

It is pointed out that an increasingly efficient use of the geostationary satellite orbit and spectrum is necessary to accommodate the growing number of planned U.S. domestic satellites, as well as those of other countries. Technical efficiency can be maximized by designing satellites in a homogeneous manner which minimizes transmission differences between satellites. However, flexibility is also needed to design domestic satellite facilities to respond to the diverse demands in a competitive market. The Federal Communication Commission (FCC) seeks to achieve a balance between these goals in their domestic satellite policies and regulations. In December 1980, the FCC authorized the construction of some 22 new domestic satellites and the launch of 18 satellites. Attention is given to orbit use policies and reduced orbital spacings.

Lepkowski, R. J.

178

Orbital varix thrombosis.  

PubMed Central

Three patients have been described with a thrombosed orbital varix. The clinical, imaging, surgical, and pathologic features of this disorder are described. A pathophysiologic mechanism has been proposed and this entity has been placed in the spectrum of orbital vascular lesions. Recommendations for the diagnostic evaluation and management of patients with thrombosed orbital varices have been offered. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 15 FIGURE 16 FIGURE 17 FIGURE 18 FIGURE 19 FIGURE 20 FIGURE 21 FIGURE 22 FIGURE 23 FIGURE 24 FIGURE 25 FIGURE 26 FIGURE 27 FIGURE 28 FIGURE 29 FIGURE 30

Bullock, J D; Goldbert, S H; Connelly, P J

1989-01-01

179

Orbital Superstructures in Spinels  

NASA Astrophysics Data System (ADS)

Orbital degrees of freedom often lead to specific types of orbital and spin ordering. Complicated and interesting superstructures are observed in B-sublattice of spinels. This is connected with the geometric frustration of this lattice and with the interconnection of edge-sharing MO6 octahedra, which is especially important for transition metals with partially-filled t2g levels. In some such systems (MgTi2O4, CuIr2S4, AlV2O4) there appears strange superstructures with the formation of spin gap states. In other cases (ZnV2O4) structural transitions, apparently connected with orbital ordering, are followed by long-range magnetic ordering. Last but not least, the famous Verwey transition in magnetite Fe3O4 leads to a very complicated structural pattern, accompanied by the appearance of ferroelectricity. In this talk I will discuss all these examples, paying main attention to an interplay of charge, spin and orbital degrees of freedom. In particular, for MgTi2O4, and CuIr2S4 we proposed the picture of orbitally-driven Peierls state [1]. Similar phenomenon can also explain situation in ZnV2O4 [2], although the corresponding superstructure has not yet been observed experimentally. Finally, I propose the model of charge and orbital ordering in magnetite [3], which uses the idea of an interplay of site- and bond-centered ordering [4] and which seems to explain both the structural data and the presence of ferroelectricity in Fe3O4 below Verwey transition. [1] D.I.Khomskii and T.Mizokawa, Phys.Rev.Lett. 94, 156402 (2005); [2] Hua Wu, T.Mizokawa and D.I.Khomskii, unpublished; [3] D.I.Khomskii, unpublished; [4] D.V.Efremov, J.van den Brink and D.I.Khomskii, Nature Mater. 3, 853 (2004)

Khomskii, Daniel

2006-03-01

180

Orbital dermoids in children.  

PubMed

Orbital dermoid cysts are benign congenital choristomas. They are common in pediatric population, developing adjacent to suture lines, most commonly located in antero-lateral fronto-zygomatic suture, and are slowly progressive. Complete surgical excision without rupture of cyst is the standard of care. Deep orbital cysts cause proptosis, require imaging, and may present a surgical challenge with a difficult approach. Rupture of the cyst leads to severe inflammatory reaction in surrounding tissues. Overall prognosis remains good with isolated reports of malignancy masquerading as dermoid cysts. PMID:16912019

Ahuja, Rakesh; Azar, Nathalie F

181

[A Roman orbital implant?].  

PubMed

During an excavation in Regensburg/Germany the skeleton of an approximately 20-year-old Roman man was found who was buried in the 3rd/4th century after Christ. A "stone" was found which fitted into the left orbit precisely. After a thorough investigation of the "stone" and with the ophthalmohistorical literature in mind an orbital "implant" as well as a petrified medical paste ("Kollyrium") could be ruled out almost with certainty. Possibly the "stone" served another medical purpose or was used for protection of the eye. PMID:23011607

Rohrbach, J M; Harbeck, M; Holzhauser, P; Tekeva-Rohrbach, C I; Mach, M; Codreanu-Windauer, S

2012-09-25

182

Local orbitals by minimizing powers of the orbital variance.  

PubMed

It is demonstrated that a set of local orthonormal Hartree-Fock (HF) molecular orbitals can be obtained for both the occupied and virtual orbital spaces by minimizing powers of the orbital variance using the trust-region algorithm. For a power exponent equal to one, the Boys localization function is obtained. For increasing power exponents, the penalty for delocalized orbitals is increased and smaller maximum orbital spreads are encountered. Calculations on superbenzene, C(60), and a fragment of the titin protein show that for a power exponent equal to one, delocalized outlier orbitals may be encountered. These disappear when the exponent is larger than one. For a small penalty, the occupied orbitals are more local than the virtual ones. When the penalty is increased, the locality of the occupied and virtual orbitals becomes similar. In fact, when increasing the cardinal number for Dunning's correlation consistent basis sets, it is seen that for larger penalties, the virtual orbitals become more local than the occupied ones. We also show that the local virtual HF orbitals are significantly more local than the redundant projected atomic orbitals, which often have been used to span the virtual orbital space in local correlated wave function calculations. Our local molecular orbitals thus appear to be a good candidate for local correlation methods. PMID:21599041

Jansík, Branislav; Høst, Stinne; Kristensen, Kasper; Jørgensen, Poul

2011-05-21

183

Local orbitals by minimizing powers of the orbital variance  

NASA Astrophysics Data System (ADS)

It is demonstrated that a set of local orthonormal Hartree-Fock (HF) molecular orbitals can be obtained for both the occupied and virtual orbital spaces by minimizing powers of the orbital variance using the trust-region algorithm. For a power exponent equal to one, the Boys localization function is obtained. For increasing power exponents, the penalty for delocalized orbitals is increased and smaller maximum orbital spreads are encountered. Calculations on superbenzene, C60, and a fragment of the titin protein show that for a power exponent equal to one, delocalized outlier orbitals may be encountered. These disappear when the exponent is larger than one. For a small penalty, the occupied orbitals are more local than the virtual ones. When the penalty is increased, the locality of the occupied and virtual orbitals becomes similar. In fact, when increasing the cardinal number for Dunning's correlation consistent basis sets, it is seen that for larger penalties, the virtual orbitals become more localthan the occupied ones. We also show that the local virtual HF orbitals are significantly more local than the redundant projected atomic orbitals, which often have been used to span the virtual orbital space in local correlated wave function calculations. Our local molecular orbitals thus appear to be a good candidate for local correlation methods.

Jansík, Branislav; Høst, Stinne; Kristensen, Kasper; Jørgensen, Poul

2011-05-01

184

Venus orbiter: Ishtar  

Microsoft Academic Search

ISHTAR or VENUS ORBITER is a mission to Venus similar to the mission Mars Express to Mars, with the use, possibly, of the same spacecraft and subsystems. This mission has been proposed to ESA for a feasibility study as a small mission (F2, F3). We shall describe here briefly the scientific objectives of the mission, and how could be implemented.

V. Formisano

2002-01-01

185

Orbital physics in RIXS  

NASA Astrophysics Data System (ADS)

In contrast to magnetism, phenomena associated with the orbital degrees of freedom in transition metal oxides had always been considered to be very difficult to observe. However, recently resonant inelastic x-ray scattering (RIXS) has established itself as a perfect probe of the orbital excitations [1] and orbital order [2] in transition metal oxides. Here we give a brief overview of these recent theoretical and experimental advances which have inter alia led to the observation of the separation of the spin and orbital degree of freedom of an electron [1, 3].[4pt] [1] J. Schlappa, K. Wohlfeld, K. J. Zhou, M. Mourigal, M. W. Haverkort, V. N. Strocov, L. Hozoi, C. Monney, S. Nishimoto, S. Singh, A. Revcolevschi, J.-S. Caux, L. Patthey, H. M. Rønnow, J. van den Brink, T. Schmitt, Nature 485, 82 (2012).[0pt] [2] P. Marra, K. Wohlfeld, J. van den Brink, Phys. Rev. Lett. 109, 117401 (2012).[0pt] [3] K. Wohlfeld, M. Daghofer, S. Nishimoto, G. Khaliullin, J. van den Brink, Phys. Rev. Lett. 107, 147201 (2011).

Wohlfeld, Krzysztof; Marra, Pasquale; Grueninger, Markus; Schmitt, Thorsten; van den Brink, Jeroen

2013-03-01

186

Orbital debris issues  

Microsoft Academic Search

Orbital debris issues fall into three major topics: Environment Definition, Spacecraft Hazard, and Space Object Management. The major issue under Environment Definition is defining the debris flux for sizes smaller (10 cm in diameter) than those tracked by the North American Aerospace Defense Command (NORAD). Sources for this size debris are fragmentation of larger objects, either by explosion or collision,

D. J. Kessler

1985-01-01

187

Lunar Exploration Orbiter  

Microsoft Academic Search

Phase 0 investigations for the German Lunar Exploration Orbiter (LEO) mission were carried out during 2007 leading to a sophisticated mission concept currently in phase A to be further detailed. Following an announcement of opportunity, also in 2007, the German Space Agency (DLR) received several proposals for the instrumentation of the LEO mission from the national science community. A board

Carsten Henselowsky; Ralf Jaumann; Uwe Kummer; Friedhelm Claasen

2008-01-01

188

Orbital Forces: Student Page  

NSDL National Science Digital Library

This activity teaches students about orbital motions and forces using a tennis ball swung by a ribbon. Students answer the question "What happens when you let the ball go?" Background information, activity procedures, and key words are provided. This activity is part of Exploring Planets in the Classroom's Planetary Properties series.

189

Lunar orbiter gravity analysis  

Microsoft Academic Search

This paper presents the results to date of the Jet Propulsion Laboratory (JPL) effort at analyzing the tracking data from the five Lunar Orbiter spacecraft. Emphasis is placed on the long-arc evaluation, to which most of the work was directed, rather than on the mascon analysis, which will be reported separately.

J. Lorell

1970-01-01

190

ARTEMIS Orbits Magnetic Moon  

NASA Video Gallery

NASA's THEMIS spacecraft have completed their mission and are still working perfectly, so NASA is re-directing the outermost two spacecraft to special orbits around the Moon. Now called ARTEMIS, they will study the solar wind and the tail of Earth's magnetosphere as well as their combined effect on the moon and its weak magnetic field.

gsfcvideo

2010-10-22

191

Smartphone Photos From Orbit  

NASA Website

These images of Earth were reconstructed from photos taken by three smartphones in orbit, or "PhoneSats." The trio of PhoneSats launched on April 21, 2013, aboard the Antares rocket from NASA's Wallops Flight Facility and ended a ...

192

Baton Orbit Model  

NSDL National Science Digital Library

Baton Orbit Model shows the trajectory of a baton-like object orbiting under the influence of a 1/r^2 force. This model was motivated by the tumbling motion of one of Saturnâs moons, Hyperion. Hyperion is the only celestial body in our solar system which exhibits chaotic tumbling. The chaotic motion is attributed to the uneven mass distribution and highly elliptical orbit of the moon. In order to model the behavior of Hyperion, we approximate its shape using a baton-like object composed of two point masses connected by a mass-less rod. This uneven mass distribution causes a net force and a net torque on its center of mass. The Baton Orbit Model was developed as a final project in a sophomore-level Computational Physics course (Phy 200) using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Barrick, Jessie

2012-06-16

193

On triangulated orbit categories  

Microsoft Academic Search

We show that the category of orbits of the bounded derived category of a hereditary category under a well-behaved autoequivalence is canonically triangulated. This answers a question by A. Buan, R. Marsh and I. Reiten which appeared in their study with M. Reineke and G. Todorov of the link between tilting theory and cluster algebras (closely related to work by

Bernhard Keller

2005-01-01

194

Pediatric orbital tumors.  

PubMed

The proper management of orbital tumors in children requires a knowledge of the lesions commonly seen in this area, in addition to the appropriate methods of investigation and treatment. A multidisciplinary approach is most beneficial in obtaining the desired results. PMID:2829096

Stefanyszyn, M A; Handler, S D; Wright, J E

1988-02-01

195

Orbital dermoid cyst  

Microsoft Academic Search

Over a thirteen year period forty patients underwent surgery to remove an orbital dermoid cyst. Cysts which became manifest after the age of three years were deeper and larger than most that were noted before that age. Three out of four epidermoid cysts appeared after the age of 17 years and had an intracranial component. The majority of cysts showed

W W Ehrlich; J E Wright

1987-01-01

196

Minimum-time orbital rendezvous between neighboring elliptic orbits  

Microsoft Academic Search

Time-optimal rendezvous maneuvers are studied. The system considered consists of a target vehicle (nonmaneuvering vehicle) in a known elliptic orbit and an interceptor vehicle (maneuvering vehicle) in a neighboring elliptic orbit such that the ratio of the distance between the two vehicles to the radius of the target-vehicle orbit is small. The interceptor vehicle has propulsive jet systems which can

K. T. Alfriend; Y. Kashiwagi

1969-01-01

197

Autonomous Aerobraking for Mars Orbiters  

NASA Astrophysics Data System (ADS)

Autonomous Aerobraking is a developing technology that will reduce cost and increase flexibility of an aerobraking orbiter around Mars. Currently in its second phase of development, autonomous aerobraking could be implemented for a 2018 Mars orbiter.

Prince, J. L.

2012-06-01

198

Measurement of Orbital Volume after Enucleation and Orbital Implantation  

PubMed Central

Introduction This article reports experience relating to the measurement of orbital volume by means of cone beam computed tomography (CBCT) and Cranioviewer program software in patients who have undergone enucleation and orbital implantation. Patients and Methods CBCT scans were made in 30 cases, 10 of which were later excluded because of various technical problems. The study group therefore consisted of 20 patients (8 men and 12 women). The longest follow-up time was 7 years, and the shortest was 1 year. In all 20 cases, the orbital volume was measured with Cranioviewer orbital program software. Slices were made in the ventrodorsal direction at 4.8 mm intervals in the frontal plane, in both bony orbits (both that containing the orbital implant and the healthy one). Similar measurements were made in 20 patients with various dental problems. CBCT scans were recorded for the facial region of the skull, containing the orbital region. The Cranioviewer program can colour the area of the slices red, and it automatically measures the area in mm. Results In 5 of the 20 cases, the first 4 or all 5 slices revealed that the volume of the operated orbit was significantly smaller than that of the healthy orbit, in 12 cases only from 1 to 3 of the slices indicated such a significant difference, and in 3 cases no differences were observed between the orbits. In the control group of patients with various dental problems, there was no significant difference between the two healthy orbits. The accuracy of the volume measurements was assessed statistically by means of the paired samples t-test. Summary To date, no appropriate method is avaliable for exact measurement of the bony orbital volume, which would be of particular importance in orbital injury reconstruction. However, the use of CBCT scans and Cranioviewer orbital program software appears to offer a reliable method for the measurement of changes in orbital volume.

Lukats, Olga; Vizkelety, Tamas; Markella, Zsolt; Maka, Erika; Kiss, Maria; Dobai, Adrienn; Bujtar, Peter; Szucs, Attila; Barabas, Jozsef

2012-01-01

199

Transient co-orbital asteroids  

Microsoft Academic Search

We analyze the orbital behavior of four new co-orbital NEOs and the Earth horseshoe object 2002 AA29. The new objects are 2001 CK32, a 3753 Cruithne-like co-orbital of Venus, 2001 GO2 and 2003 YN107, two objects with motion similar to 2002 AA29. 2001 CK32 is on a compound orbit. The asteroid reverses its path when the mean longitude difference is

R. Brasser; K. A. Innanen; M. Connors; C. Veillet; P. Wiegert; Seppo Mikkola; P. W. Chodas

2004-01-01

200

Optimal periodic relative orbit and rectilinear relative orbits with eccentric reference orbits  

NASA Astrophysics Data System (ADS)

The problem of two-body linearized periodic relative orbits with eccentric reference orbits is studied in this paper. The periodic relative orbit in the target-orbital coordinate system can be used in fly-around and formation-flying orbit design. Based on the closed-form solutions to the Tschauner-Hempel equations, the initial condition for periodic relative orbits is obtained. Then the minimum-fuel periodic-orbit condition with a single impulse is analytically derived for given initial position and velocity vectors. When considering the initial coasting time, the impulse position of the global minimum-fuel periodic orbit is proved to be near to the perigee of the target and can be obtained by numerical optimization algorithms. Moreover, the condition for a special periodic orbit, i.e., the rectilinear relative orbit in the target-orbital frame, is obtained. Numerical simulations are used to demonstrate the efficacy of the method, and show the geometry of the periodic relative orbit and the rectilinear relative orbit.

Zhang, Gang; Zhou, Di; Sun, Zhaowei; Cao, Xibin

2013-10-01

201

Examination of trajectories between low planetary orbits and circulation orbits  

NASA Astrophysics Data System (ADS)

Circulating orbits have been investigated to provide regular periodic transfers between the Earth and Mars. The circulating orbits pass close enough to each planet to be considered hyperbolic in planetocentric frame. The large spacecraft (CASTLE) in the circulating orbit is resupplied by a smaller 'Taxi' spacecraft leaving a low planetary orbit. The Taxi follows an optimal three-impulse patched-conic trajectory to travel from its spaceport to the large spacecraft following a hyperbolic fly-by. Examining the parameters of the situation produces a Delta V profile for each planetary fly-by of the circulating orbit.

Knoedler, Andrew J.

202

Prospective Ukrainian lunar orbiter mission  

Microsoft Academic Search

Ukraine has launch vehicles that are able to deliver about 300 kg to the lunar orbit. Future Ukrainian lunar program may propose a polar orbiter. This orbiter should fill principal information gaps in our knowledge about the Moon after Clementine and Lunar Prospector missions and the future missions, like Smart-1, Lunar-A, and Selene. We consider that this can be provided

Y. Shkuratov; L. Litvinenko; V. Shulga; Y. Yatskiv; V. Kislyuk

2002-01-01

203

Semiclassical quantization using diffractive orbits  

Microsoft Academic Search

Diffraction, in the context of semiclassical mechanics, describes the manner in which quantum mechanics smooths over discontinuities in classical mechanics. Semiclassical quantization then requires the inclusion of diffractive periodic orbits in addition to classical periodic orbits. In this Letter we construct the corresponding diffractive zeta function and apply it to a scattering problem which has only diffractive periodic orbits. We

Niall D. Whelan

1996-01-01

204

Blepharoplasty revealing orbital lymphoma.  

PubMed

Blepharoplasty is a frequent request in consultations of plastic surgery. Patients are often presenting with a progressive swelling of the eyelids. For functional or aesthetic reasons, we commonly perform a superior and/or inferior blepharoplasty to correct this problem. We present the case of a 72-year-old woman who consulted us with a prominent unattractive swelling of both lower eyelids. Because of the atypical and suspicious presentation, supplementary examinations were conducted, and the fat was also sent for analysis. A diagnosis of unilateral orbital lymphoma was obtained. The patient was treated as a primarily localized lymphoma with a positive outcome. When correctly diagnosed and treated, orbital lymphomas can have a very good prognosis. PMID:22214799

Marival, Talia; Carpentier, Séverine; Vandaele, Shiran; de Fontaine, Serge

2013-03-01

205

Orbital changes and climate  

Microsoft Academic Search

At the 41,000-period of orbital tilt, summer insolation forces a lagged response in northern ice sheets. This delayed ice signal is rapidly transferred to nearby northern oceans and landmasses by atmospheric dynamics. These ice-driven responses lead to late-phased changes in atmospheric CO2 that provide positive feedback to the ice sheets and also project ‘late’ 41-K forcing across the tropics and

William F. Ruddiman

2006-01-01

206

The Solar Orbiter mission  

NASA Astrophysics Data System (ADS)

The ESA/NASA Solar Orbiter mission will address the central question of heliophysics: How does the Sun create and control the heliosphere? The heliosphere represents a uniquely accessible domain of space, where fundamental physical processes common to solar, astrophysical and laboratory plasmas can be studied under conditions impossible to reproduce on Earth and unfeasible to observe from astronomical distances. In this paper, we present a brief overview of the mission.

Müller, Daniel; St. Cyr, O. Chris

2013-09-01

207

Orbital cystic neurinoma  

Microsoft Academic Search

Summary ¶A 64-year-old woman presented with a 6-month history of exophthalmus of her right eye. She had no neurological deficit except for the exophthalmus and numbness in the right side of her forehead (frontal nerve territory). Neuro-imaging demonstrated a cystic mass in the right orbit. The tumour was totally removed by microsurgical transcranial surgery. The histological diagnosis was neurinoma. The

J. Tokugawa; Y. Nakao; K. Mori; M. Maeda

2003-01-01

208

Orbital and physical parameters of the spectroscopic binary HD37737  

NASA Astrophysics Data System (ADS)

We report the physical and orbital parameters of the visible component of the spectroscopic binary HD37737 ( m V = 8.03). The observations were performed with the 1.2-m telescope of the Kourovka Astronomical Observatory of the Ural Federal University in 2012 and the 6-m BTA telescope of the SAO RAS in 2007 and 2009. Radial velocities were measured separately from each spectral line of the list by the cross-correlation method with a synthetic spectrum. The latter was calculated using the grids of non-LTE model atmospheres with solar chemical compositions. A significant difference in the epochs of observations (2005-2012) allowed to refine the orbital period of the star (7{·/d}84705) and the orbital elements of the binary system. We obtained an estimate of the mass function f( m) = 0.23 ± 0.02 M ?. The best agreement between the synthetic and observed spectra is achieved at T eff = 30 000 K and log g = 3.50 according to the observations on both instruments. The obtained parameters correspond to a star of spectral type O9.5 III, with mass estimated at 26 ± 2 M ?. The minimum mass estimate of the secondary component of the binary is 6.2 ± 0.5 M ?. We have discovered a fact that the velocities, obtained from different spectral lines, differ, which is typical for giant stars. Engaging additional spectra, obtained in 2005 with the 2.1-m KPNO telescope, we investigated the effect of this fact on the estimate of the speed of the system's center of mass. The difference in the velocities of various lines is approximately the same in the spectra, obtained at all the three instruments. The obtained ratios suggest that the deeper layers of the atmosphere of the star are moving with a greater velocity than the outer layers. Depending on the line, the estimate of the heliocentric velocity of the binary's center of mass varies in the range from -11 to 1 km/s.

Alexeeva, S. A.; Sobolev, A. M.; Gorda, S. Yu.; Yushkin, M. V.; McSwain, V.

2013-04-01

209

Myeloma-associated orbital amyloidosis.  

PubMed

Orbital amyloidosis is extremely rare and may be localized finding or secondary to a systematic process. The majority of the patients with orbital amyloidosis have primary localized disease. We report a 55 year old male with multiple myeloma and secondary amyloidosis who presented with incidental bilateral orbital masses on MRI. Biopsy revealed amyloid deposition. We review the previously published cases of the orbital amyloidosis secondary to systematic light chain (AL) amyloidosis, including one patient with multiple myeloma. The clinical signs and symptoms, histopathologic findings, and radiographic features of orbital amyloidosis are discussed. PMID:20572755

Goshe, Jeff M; Schoenfield, Lynn; Emch, Todd; Singh, Arun D

2010-06-23

210

Late correction of orbital deformities.  

PubMed

Orbital fractures are some of the most challenging injuries the oral surgeon deals with on a daily basis. Delay of the treatment of orbital fractures impacts the final result. Late orbital reconstruction is sometimes necessary for inadequate primary reconstruction or for severe injuries with adequate primary reconstruction. Healing and wound contraction make secondary reconstruction more difficult to restore the orbital contents back to normal. There are different materials available for orbital reconstruction, and there is no consensus about which is best. Early surgical intervention may improve the ultimate outcome, but identifying patients at risk of late complications is difficult. PMID:23017201

Palmieri, Celso F; Ghali, G E

2012-09-24

211

Asteroid-type orbit evolution near the 5:2 resonance  

NASA Astrophysics Data System (ADS)

In this case of the 5:2 commensurability with the motion of Jupiter, an asteroid can reach the orbits of Mars, Earth, and Venus when eccentricity e is greater than 0.41, 0.65, and 0.74, respectively. For individual fictitious asteroids, Ipatov and Yoshikawa obtained a growth in e from 0.15 to 074-0.76. Rates of changes in orbital orientations are different for Mars, Earth, Venus, and the asteroid. Therefore, for corresponding values of e, the asteroid could encounter these planets and leave the gap at those encounters. In order to investigate this hypothesis of the 5:2 Kirkwood gap formation, Ipatov studied the regions of initial data for which the eccentricities of asteroids located near the 5:2 commensurability exceeded 0.41 during evolution. The orbit evolution for 500 fictitious asteroids was investigated by numerical integration of the complete (unaveraged) equations of motion for the three-body problem (Sun-Jupiter-asteroid). The equations of motion were integrated in the time intervals T is greater than or equal to 5(10)3tJ (tJ is the heliocentric orbital period of Jupiter) in the planar model, T is greater than or equal to 104tJ at initial inclination 5 deg is less than or equal to i0 is less than or equal to 20 deg and T = 105tJ at i0 = 40 deg. The larger interval T was taken at i0 = 40 deg because in this case for the majority of runs maximum values of e and i were reached in the time delta(t) is greater than 2(10)4tJ.

Ipatov, S. I.

1992-12-01

212

A heliocentric view of leptin.  

PubMed

Leptin is significantly broadening our understanding of the mechanisms underlying neuroendocrine function. Initially, based on a rather static view of the hormone, most investigations focused on the effects of leptin on food intake control and body-weight homeostasis, with attention primarily focused on the implications of leptin as a lipostatic factor and central satiety agent. However, the almost ubiquitous distribution of leptin receptors in peripheral tissues provided a fertile area for investigation and a more dynamic view of leptin started to unfold. This adipocyte-derived circulating peptidic hormone, with a tertiary structure resembling that of members of the long-chain helical cytokine family, has generated an enormous interest in the interaction as well as integration between brain targets and peripheral signals. Considerable evidence for systemic effects of leptin on specific tissues and metabolic pathways indicates that leptin operates both directly and indirectly to orchestrate complex pathophysiological processes. Disentangling the biochemical and molecular mechanisms in which leptin is involved represents one of the major challenges ahead. PMID:11681805

Frühbeck, G

2001-08-01

213

Counter-Orbitals: Another Class of Co-Orbitals  

NASA Astrophysics Data System (ADS)

Co-orbital companions share the same orbital period and semi-major axis about a primary (star or planet). Heretofore there have been three recognized classes of co-orbitals: (1) Trojans librate in tadpole-shaped orbits about the equilateral Lagrange points L4 and L5, 60 degrees ahead of or behind the secondary (planet or satellite). (2) Horse-shoe companions librate about both L4 and L5, as well as the L3 Lagrange point diametrically opposite the secondary. (3) ``Quasi-satellites'' appear to be in distant retrograde orbits about the secondary, but actually are in prograde orbits about the primary with the same period as the secondary. Quasi-satellite orbits lie outside the secondary's Hill sphere, and enclose both L1 and L2, and sometimes L4 and L5 as well. In addition, some asteroids and comets are found in hybrid orbits which alternate among the above three classes, or combine some of their features. New research now reveals a fourth class of co-orbitals, which does not appear to be known before, and may be called ``counter-orbitals''. Imagine reversing the inertial velocity of a distant quasi-satellite. Then it remains in orbit about the primary, with the same period, semi-major axis, eccentricity, and orbital plane, although retrograde. But instead of remaining relatively close to the secondary, now it passes the secondary twice per orbit, near periapsis and apoapsis. The attractive impulses at these conjunctions tend to stabilize this arrangement. Numerical simulations of the general three-body problem verify that counter-orbitals can persist for over 10,000 orbits, with small vertical excursions, but a wide range of eccentricities and mass ratios. For example, Charon can maintain counter-orbital companions at least up to 3 percent of its own mass, in eccentric orbits extending from about 7050 km out to 41700 km from the center of Pluto. This may present a collision hazard to the New Horizons spacecraft.

Dobrovolskis, Anthony R.

2012-10-01

214

Electric Propulsion Orbital Platform  

NASA Astrophysics Data System (ADS)

This paper describes the Electric Propulsion Orbital Platform (EPOP), of which the primary objective is to provide an instrumented platform for testing electric propulsion devices in space. It is anticipated that the first flight, EPOP-1, will take place on the Shuttle-deployed Wake Shield Facility in 1996, and will be designed around a commercial 1.8 kW arcjet system which will be operated on gaseous hydrogen propellant. Specific subsystems are described, including the arcjet system, the propellant and power systems, and the diagnostics systems.

Friedly, V. J.; Ruyten, Wilhelmus M.; Litchford, R. J.; Garrison, G. W.

1993-01-01

215

Lunar Exploration Orbiter (LEO)  

NASA Astrophysics Data System (ADS)

The Moon is an integral part of the Earth-Moon system, it is a witness to more than 4.5 b. y. of solar system history, and it is the only planetary body except Earth for which we have samples from known locations. The Moon is our closest companion and can easily be reached from Earth at any time, even with a relatively modest financial budget. Consequently, the Moon was the first logical step in the exploration of our solar system before we pursued more distant targets such as Mars and beyond. The vast amount of knowledge gained from the Apollo and other lunar missions of the late 1960's and early 1970's demonstrates how valuable the Moon is for the understanding of our planetary system. Even today, the Moon remains an extremely interesting target scientifically and technologically, as ever since, new data have helped to address some of our questions about the Earth-Moon system, many questions remained. Therefore, returning to the Moon is the critical stepping-stone to further exploring our immediate planetary neighborhood. In this concept study, we present scientific and technological arguments for a national German lunar mission, the Lunar Explorations Orbiter (LEO). Numerous space-faring nations have realized and identified the unique opportunities related to lunar exploration and have planned missions to the Moon within the next few years. Among these missions, LEO will be unique, because it will globally explore the Moon in unprecedented spatial and spectral resolution. LEO will significantly improve our understanding of the lunar surface composition, surface ages, mineralogy, physical properties, interior, thermal history, gravity field, regolith structure, and magnetic field. The Lunar Explorations Orbiter will carry an entire suite of innovative, complementary technologies, including high-resolution camera systems, several spectrometers that cover previously unexplored parts of the electromagnetic spectrum over a broad range of wavelengths, microwave and radar experiments, a very sensitive magnetometer and gradiometer, a subsatellite, and a state-of-the-art optical communication system. The Lunar Explorations Orbiter concept is technologically challenging but feasible, and will gather unique, integrated, interdisciplinary data sets that are of high scientific interest and will provide an unprecedented new context for all other international lunar missions. In fact, the Lunar Explorations Orbiter will further establish Germany as a leader among space-faring nations and will demonstrate expertise and technological know-how, which is "Made in Germany". With its high visibility, LEO will foster the growing acceptance of space exploration in Germany and will capture the imagination of the general public.

Jaumann, R.; Spohn, T.; Hiesinger, H.; Jessberger, E. K.; Neukum, G.; Oberst, J.; Helbert, J.; Christensen, U.; Keller, H. U.; Mall, U.; Böhnhardt, H.; Hartogh, P.; Glassmeier, K.-H.; Auster, H.-U.; Moreira, A.; Werner, M.; Pätzold, M.; Palme, H.; Wimmer-Schweingruber, R.; Mandea, M.; Lesur, V.; Häusler, B.; Hördt, A.; Eichentopf, K.; Hauber, E.; Hoffmann, H.; Köhler, U.; Kührt, E.; Michaelis, H.; Pauer, M.; Sohl, F.; Denk, T.; van Gasselt, S.

2007-08-01

216

Orbital YORP and asteroid orbit evolution, with application to Apophis  

NASA Astrophysics Data System (ADS)

Photon thrust from shape alone can produce quasi-secular changes in an asteroid's orbital elements. An asteroid in an elliptical orbit with a north-south shape asymmetry can steadily alter its elements over timescales longer than one orbital trip about the Sun. This thrust, called here orbital YORP (YORP = Yarkovsky-O'Keefe-Radzievskii-Paddack), operates even in the absence of thermal inertia, which the Yarkovsky effects require. However, unlike the Yarkovsky effects, which produce secular orbital changes over millions or billions of years, the change in an asteroid's orbital elements from orbital YORP operates only over the precession timescale of the orbit or of the asteroid's spin axis; this is generally only thousands or tens of thousands of years. Thus while the orbital YORP timescale is too short for an asteroid to secularly journey very far, it is long enough to warrant investigation with respect to 99942 Apophis, which might conceivably impact the Earth in 2036. A near-maximal orbital YORP effect is found by assuming Apophis is without thermal inertia and is shaped like a hemisphere, with its spin axis lying in the orbital plane. With these assumptions orbital YORP can change its along-track position by up to ±245 km, which is comparable to Yarkovsky effects. Though Apophis' shape, thermal properties, and spin axis orientation are currently unknown, the practical upper and lower limits are liable to be much less than the ±245 km extremes. Even so, the uncertainty in position is still likely to be much larger than the ˜0.5 km "keyhole" Apophis must pass through during its close approach in 2029 in order to strike the Earth in 2036.

Rubincam, David Parry

2007-12-01

217

Orbital physics (Communication arising): Experimental quest for orbital waves  

Microsoft Academic Search

One challenge in condensed-matter physics is the experimental confirmation of a new kind of elementary excitation - orbital waves, or orbitons, which are predicted to exist in an orbitally ordered state. Saitoh et al. have observed three peaks at 160, 144 and 126 meV in the Raman scattering of orbitally ordered lanthanum manganate (LaMnO3), and interpret these as evidence of

M. Grüninger; R. Rückamp; M. Windt; P. Reutler; C. Zobel; T. Lorenz; A. Freimuth; A. Revcolevschi

2002-01-01

218

The Toasty Solar System: Inside Earth's Orbit  

Microsoft Academic Search

In 2011 the Canadian Space Agency will launch the NEOSSat spacecraft (Near-Earth Object Surveillance Satellite). This space telescope will survey the sky at low solar elongations for 1-2 years and be especially sensitive to near-Earth objects (NEOs) with semimajor axes smaller than 1 AU, including objects at heliocentric distances as small as that of Venus. The search will be optimized

Sarah Greenstreet; H. Ngo; B. Gladman

2010-01-01

219

The orbital surgeon.  

PubMed Central

While the number of orbital surgeons is limited, it is hoped these can be recognized and patients referred to them by ophthalmologists not interested or trained in that specialty. Let the orbital surgeon determine whether he can handle the problem in 1 to 2 days, or whether a neurosurgeon should do the procedure or make it a joint effort. It may well involve other specialty team effort approaches. It is essential to have an understanding of x-rays, CT, angiography, and MRI techniques and films. Sit with these specialists to learn more and help to avoid negative, misdiagnosis reports in the interest of the patient. Use judgement in helping the patient decide on ophthalmic or the more extensive neurosurgical approach after careful study and what is in their best interest. The team approach is used in well established medical centers with the ophthalmologist and neurosurgeon (or other specialist) working together in the best interest of the patient. This is more interesting and keeps the ophthalmologist in the mainstream of medicine. Images FIGURE 1 A FIGURE 1 B FIGURE 1 C FIGURE 2 FIGURE 3 A FIGURE 3 B FIGURE 3 C FIGURE 3 D FIGURE 4 A FIGURE 4 B FIGURE 5 A FIGURE 5 B FIGURE 6 A FIGURE 6 B FIGURE 7 A FIGURE 7 B FIGURE 7 C FIGURE 8 A FIGURE 8 B FIGURE 9

Kennedy, R E

1988-01-01

220

Geostationary versus non geostationary orbits  

NASA Astrophysics Data System (ADS)

The issue of which satellite orbit, such as low earth orbit, medium earth orbit, highly elliptical orbit, geosynchronous orbit, etc., is best for a particular telecommunications role is not always straightforward. The technical, operational, financial, service, and reliability considerations must all be carefully assessed and detailed trade-off analysis undertaken. This article provides in some detail the type of methodology that can be utilized to conclude which particular set of orbital parameters would seem to be optimum for various missions. Ironically, many of the trade-off considerations today are similar to those some 30 years ago when the field of satellite communications was getting started. One major difference today is that satellite launch and operation is much more reliable. The general methodology presented here should be adaptable to addressing almost any proposed satellite system design and its optimum deployment.

Pritchard, Wilbur

221

Geostationary Earth Orbit Satellite Model  

NSDL National Science Digital Library

The Geostationary Earth Orbit Satellite Model is a simple angular velocity model that uses Java3D for a realistic visualization of satellites in geostationary orbits. Students can view and explore the behavior of geostationary orbits, non-geostationary orbits, and non-physical orbits. This model tests the Java 3D implementation of the EJS 3D library. A warning message will appear if the Java 3D library is not available. The Geostationary Earth Orbit Satellite Model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Wee, Loo K.

2012-04-08

222

The effects of outgassing jets on the rotation of a comet nucleus and on the trajectory of an orbiting spacecraft  

NASA Astrophysics Data System (ADS)

An outgassing jet model is presented in this thesis in support of spacecraft navigation for future missions to comets. The outgassing jet is modelled as an emission cone while the comet nucleus is modelled as a uniform density triaxial ellipsoid. The heliocentric orbit motion as well as in the strength of the outgassing jet are accounted for in the equations of motion. This model is used for predicting the rotational evolution of a comet nucleus as a result the outgassing jets' reactive torques as well as for simulation of an orbiting spacecraft's trajectory through jet passages and the estimation of the physical outgassing properties of jets from perturbations to the spacecraft's motion. A model for the rotational evolution of a comet nucleus is presented and predicts possible levels of rotational excitation for a comet nucleus under torques produced by multiple discrete outgassing jets located on the surface. An analytical theory for the secular solution to the rotational motion of comets with an axis of symmetry is derived and used to predict rotational state changes over multiple perihelion passages. A method of characterizing the comet nucleus dynamics to predict the end state of the rotation is found from the averaged equations. Applications of these analytical results to predict the stochastic evolution of a comet nucleus rotation are outlined. This thesis also identifies and analyzes stable Sun synchronous orbits in a Hill rotating frame which can be applied to any small body in the solar system. The stability of these orbits is due to the inclusion of solar radiation pressure effects. The stability of the orbits in terms of escaping the comet is analyzed though construction of zero-velocity curves and the use of spectral analysis. The effect of orbital perturbations from outgassing jets on the stability criterion are also considered in the stability analysis of a spacecraft in orbit about a comet. Once these orbits have been identified, the effects of a non-spherical body are explored. In addition, impulsive and finite burn control schemes to restrict a stable orbit's motion are determined, showing that it is feasible to implement a form of orbital hovering in the terminator plane of a comet.

Byram, Sharyl M.

223

Orbital myositis: Diagnosis and management  

Microsoft Academic Search

Orbital myositis is an inflammatory process that primarily involves the extraocular muscles and most commonly affects young\\u000a adults in the third decade of life, with a female predilection. Clinical characteristics of orbital myositis include orbital\\u000a and periorbital pain, ocular movement impairment, diplopia, proptosis, swollen eyelids, and conjunctival hyperemia. The most\\u000a common presentation is acute and unilateral, which initially responds to

Roberta M. S. Costa; Oana M. Dumitrascu; Lynn K. Gordon

2009-01-01

224

CBERS-2 LEOP Orbit Analysis  

Microsoft Academic Search

This work presents an analysis of CBERS-2 orbit during LEOP (Launching and Early Orbit Phase), including the main aspects related to the INPE´s pass to pass improvement of the initial orbit determination process application. This is the second of four sun-synchronous earth observation satellites foreseen to be developed and manufactured within a cooperation program between Brazil and China. A short

V. Orlando; H. K. Kuga; J. Tominaga

2004-01-01

225

Intrinsic stability of periodic orbits  

Microsoft Academic Search

Families of orbits of a conservative, two degree-of-freedom system are represented by an unsteady velocity field with components u(x,y,t) and v(x,y,t). It is shown that a necessary condition for stable periodic orbits is satisfied when the orbit-averaged divergence is zero, which results in bounded normal variations. A sufficient condition for stability is derived from the requirement that tangential variations do

Michael E. Hough

1987-01-01

226

Ancient schwannoma of the orbit.  

PubMed

Schwannoma, also referred to as neurilemmoma or peripheral neurinoma, is an unusual orbital benign tumour that may pose diagnostic challenges. Awareness of the clinical features that may be associated with the tumour and prompt surgical excision with histopathologic examination enable correct diagnosis. The authors describe a progressively increasing inferolateral orbital mass in a 32-year-old patient that was demonstrated to be an orbital ancient schwannoma. PMID:23316621

Pecorella, I; Toth, J; Lukats, O

2012-08-01

227

Orbiter Servicer Rendezvous Simulation (ORSIM)  

NASA Astrophysics Data System (ADS)

Orbiter Servicer Rendezvous Simulation (ORSIM) is an automated tool that simulates sequential transfer maneuvers of an orbital maneuvering vehicle (OMV) transporting orbital replaceable units from a space-based depot, or logistics platform, to higher altitude SDI sdatellites. ORSIM calculates OMV energy expenditures (velocity changes) and event histories for various combinations of user-selected orbital transfer maneuvers. Additionally, ORSIM determines the optimal configuration/quantities of logistics platforms and OMVs which conform to the dynamics of differential nodal precession, given user-prescribed values of the scheduled maintenance cycle and required servicing times. ORSIM is coded in FORTRAN-77 and is resident on an IBM PC/AT.

Amato, Amiel; Hoffman, Mickie D.

228

Lunar Reconnaissance Orbiter  

NASA Astrophysics Data System (ADS)

NASA's Lunar Reconnaissance Orbiter (LRO) plans to launch in October 2008 with a companion secondary impactor mission, LCROSS, as the inaugural missions for the Exploration System Mission Directorate. LRO is a pathfinder whose objective is to obtain the needed information to prepare for eventual human return to the Moon. LRO will undertake at least one baseline year of operation with additional extended mission phase sponsored by NASA's Science Mission Directorate. LRO will employ six individual instruments to produce accurate maps and high-resolution images of future landing sites, to assess potential lunar resources, and to characterize the radiation environment. LRO will also test the feasibility of one advanced technology demonstration package. The LRO payload includes: Lunar Orbiter Laser Altimeter (LOLA) which will determine the global topography of the lunar surface at high resolution, measure landing site slopes, surface roughness, and search for possible polar surface ice in shadowed regions; Lunar Reconnaissance Orbiter Camera (LROC) which will acquire targeted narrow angle images of the lunar surface capable of resolving meter-scale features to support landing site selection, as well as wide-angle images to characterize polar illumination conditions and to identify potential resources; Lunar Exploration Neutron Detector (LEND) which will map the flux of neutrons from the lunar surface to search for evidence of water ice, and will provide space radiation environment measurements that may be useful for future human exploration; Diviner Lunar Radiometer Experiment (DLRE) which will chart the temperature of the entire lunar surface at approximately 300 meter horizontal resolution to identify cold-traps and potential ice deposits; Lyman-Alpha Mapping Project (LAMP) which will map the entire lunar surface in the far ultraviolet. LAMP will search for surface ice and frost in the polar regions and provide images of permanently shadowed regions illuminated only by starlight; Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which will investigate the effect of galactic cosmic rays on tissue-equivalent plastics as a constraint on models of biological response to background space radiation. The technology demonstration is an advanced radar (mini-RF) that will demonstrate X- and S-band radar imaging and interferometry using a light-weight synthetic aperture radar.

Morgan, T.; Chin, G.

2007-08-01

229

Axial rotation, orbital revolution and solar spin-orbit coupling  

Microsoft Academic Search

The orbital motion of the Sun has been linked with solar variability, but the underlying physics remains unknown. A coupling of the solar axial rotation and the barycentric orbital revolution might account for the relationships found. Some recent published studies addressing the physics of this problem have made use of equations from rotational physics in order to model particle motions.

James H. Shirley

2006-01-01

230

Orbital Fluctuations and Orbital Flipping in RVO3 Perovskites  

SciTech Connect

The effect of the average A-site ionic radius hIRi and variance on the orbital and magnetic order in R3+-doped YVO3 was studied in Y1-xLaxVO3 and Y1-x(La0.2337Lu0.7663)xVO3 with fixed . The orbital flipping temperature T_CG increases nonlinearly with increasing R-site variance, indicating that the V-O-V bond angle is not the primary driving force stabilizing the C-type orbitally ordered phase. The suppressed thermal conductivity in the G-type orbitally ordered phase signals some remaining orbital randomness that is enhanced by t2 and et hybridization in 3T_1g site symmetry.

Yan, J.-Q. [Ames Laboratory; Zhou, J.-S. [University of Texas, Austin; Goodenough, J. B. [University of Texas, Austin; Ren, Y. [Argonne National Laboratory (ANL); Cheng, J. G. [Harbin Institute of Technology; Zarestky, Jerel L [ORNL; Garlea, Vasile O [ORNL; Liobet, A. [Los Alamos National Laboratory (LANL); Zhou, H. D. [University of Texas, Austin; Sui, Y. [Harbin Institute of Technology; Su, W. H. [Harbin Institute of Technology; McQueeney, R. J. [Ames Laboratory

2007-01-01

231

PyORBIT: A Python Shell For ORBIT  

SciTech Connect

ORBIT is code developed at SNS to simulate beam dynamics in accumulation rings and synchrotrons. The code is structured as a collection of external C++ modules for SuperCode, a high level interpreter shell developed at LLNL in the early 1990s. SuperCode is no longer actively supported and there has for some time been interest in replacing it by a modern scripting language, while preserving the feel of the original ORBIT program. In this paper, we describe a new version of ORBIT where the role of SuperCode is assumed by Python, a free, well-documented and widely supported object-oriented scripting language. We also compare PyORBIT to ORBIT from the standpoint of features, performance and future expandability.

Jean-Francois Ostiguy; Jeffrey Holmes

2003-07-01

232

Orbital Fluctuations and Orbital Flipping in RVO3 Perovskites  

NASA Astrophysics Data System (ADS)

The effect of the average R-site ionic radius ?IR? and variance on the orbital and magnetic order in R3+-doped YVO3 was studied in Y1-xLaxVO3 and Y1-x(La0.2337Lu0.7663)xVO3 with fixed ?IR?. The orbital flipping temperature TCG increases nonlinearly with increasing R-site variance, indicating that the V-O-V bond angle is not the primary driving force stabilizing the C-type orbitally ordered phase. The suppressed thermal conductivity in the G-type orbitally ordered phase signals some remaining orbital randomness that is enhanced by t2 and et hybridization in T1g3 site symmetry.

Yan, J.-Q.; Zhou, J.-S.; Goodenough, J. B.; Ren, Y.; Cheng, J. G.; Chang, S.; Zarestky, J.; Garlea, O.; Liobet, A.; Zhou, H. D.; Sui, Y.; Su, W. H.; McQueeney, R. J.

2007-11-01

233

Orbital xanthogranuloma in adults.  

PubMed Central

The onset of periorbital xanthogranuloma in adults is rare and may be accompanied by haematological abnormalities and malignancy. The appearance of the eyelid lesions is virtually diagnostic, producing readily recognisable diffuse, yellow plaques, and affected patients should be investigated and reviewed regularly for systemic disease. Three cases are described, in which periorbital cutaneous plaques were associated with abnormal tissues in the superior part of the orbit; these abnormal tissues caused displacement or restricted movement of the globe or upper eyelid. The possibility that two cases represent a necrobiotic type of xanthogranuloma is presented. Nine years after the onset of xanthogranuloma one patient developed non-Hodgkin's lymphoma. A multiple-drug regimen of systemic chemotherapy, given for lymphoma, caused a marked clinical reduction in the periorbital xanthogranuloma. Images

Rose, G. E.; Patel, B. C.; Garner, A.; Wright, J. E.

1991-01-01

234

Exploratory orbit analysis  

SciTech Connect

Unlike the other documents in these proceedings, this paper is neither a scientific nor a technical report. It is, rather, a short personal essay which attempts to describe an Exploratory Orbit Analysis (EOA) environment. Analyzing the behavior of a four or six dimensional nonlinear dynamical system is at least as difficult as analyzing events in high-energy collisions; the consequences of doing it badly, or slowly, would be at least as devastating; and yet the level of effort and expenditure invested in the latter, the very attention paid to it by physicists at large, must be two orders of magnitude greater than that given to the former. It is difficult to choose the model which best explains the behavior of a physical device if one does not first understand the behavior of the available models. The time is ripe for the development of a functioning EOA environment, which I will try to describe in this paper to help us achieve this goal.

Michelotti, L.

1989-03-01

235

TOPEX orbital radiation study  

SciTech Connect

The space radiation environment of the TOPEX spacecraft is investigated. A single trajectory was considered. The external (surface incident) charged particle radiation, predicted for the satellite, is determined by orbital flux integration for the specified trajectory. The latest standard models of the environment are used in the calculations. The evaluation is performed for solar maximum conditions. The spacecraft exposure to cosmic rays of galactic origin is evaluated over its flight path through the magnetosphere in terms of geomagnetic shielding effects, both for surface incident heavy ions and for particles emerging behind different material thickness. Limited shielding and dose evaluations are performed for simple infinite slab and spherical geometries. Results, given in graphical and tabular form, are analyzed, explained, and discussed. Conclusions are presented and commented on.

Stassinopoulos, E.G.; Barth, J.M.

1984-04-01

236

Orbital exenteration--simplified.  

PubMed Central

In summary, a simplified technique of orbital exenteration has been presented. Results, with complications, in eleven cases have been described. The advantages of the operative method described are: (1) full thickness skin provides better cushion for self-retaining prosthesis, (2) skin with intact blood supply is much less likely to be rejected, (3) no donor site with added discomfort and care, (4) local recurrence of neoplasm is easily detected, (5) operating time shortened and (6) favorable patient acceptance. Images FIGURE 8 A FIGURE 8 B FIGURE 9 FIGURE 10 FIGURE 11 A FIGURE 11 B FIGURE 11 C FIGURE 11 D FIGURE 12 FIGURE 13 A FIGURE 13 B FIGURE 14 A FIGURE 14 B FIGURE 15 FIGURE 16 FIGURE 17

Coston, T O; Small, R G

1981-01-01

237

Orbital science's 'Bermuda Triangle'  

NASA Astrophysics Data System (ADS)

The effects of a part of the inner Van Allen belt lying closest to the earth, known as the South Atlantic Anomaly (SAA) upon spacecraft including the Hubble Space Telescope (HST), are discussed. The area consists of positively charged ions and electrons from the Van Allen Belt which become trapped in the earth's dipole field. Contor maps representing the number of protons per square centimeter per second having energies greater than 10 million electron volts are presented. It is noted that the HST orbit causes it to spend about 15 percent of its time in the SAA, but that, unlike the experience with earlier spacecraft, the satellite's skin, internal structure, and normal electronic's packaging provides sufficient protection against eletrons, although some higher energy protons still get through. Various charged particle effects which can arise within scientific instruments including fluorescence, Cerenkov radiation, and induced radioactivity are described.

Sherrill, Thomas J.

1991-02-01

238

[Rhabdomyosarcoma of the orbit].  

PubMed

The authors evaluated 9 years' experience with the diagnosis and treatment of embryonic rhabdomyosarcoma of the orbit in children. They evaluated in detail a group of 5 children treated and followed up for 1-9 years. Due to comprehensive surgical, radiation and chemotherapeutic treatment all patients survive and in 80% the visual function is preserved. For differential diagnostic problems, with regard to the variable manifestation of rhabdomyosarcoma which may imitate orbitocellulitis, chalaseon, epibulbar lipodermoid or papilloma, the authors emphasize the importance of rapid primary diagnosis by NMR and biopsy. In the treatment they appreciate greatly a combination of radiotherapy and chemotherapy which is a modern trend and can eradicate the tumour without radical surgery. PMID:9213517

Gerinec, A; Chynoranský, M; Galbavý, S

1997-02-01

239

Photometry of 2006 RH{120}: an asteroid temporary captured into a geocentric orbit  

NASA Astrophysics Data System (ADS)

Aims: From July 2006 to July 2007 a very small asteroid orbited the Earth within its Hill sphere. We used this opportunity to study its rotation and estimate its diameter and shape. Methods: Due to its faintness, 2006 RH{120} was observed photometrically with the new 10-m SALT telescope at the SAAO (South Africa). We obtained data on four nights: 11, 15, 16, and 17 March 2007 when the solar phase angle remained almost constant at 74°. The observations lasted about an hour each night and the object was exposed for 7-10 s through the “clear” filter. Results: From the lightcurves obtained on three nights we derived two solutions for a synodical period of rotation: P1 = 1.375 ± 0.001 min and P2 = 2.750 ± 0.002 min. The available data are not sufficient to choose between them. The absolute magnitude of the object was found to be H = 29.9 ± 0.3 mag (with the assumed slope parameter G = 0.25) and its effective diameter D = 2-7 m, depending on the geometric albedo pV (with the most typical near-Earth asteroids albedo pV = 0.18 its diameter would be D = 3.3 ± 0.4 m). The body has an elongated shape with the a/b ratio greater than 1.4. It probably originates in low-eccentricity Amor or Apollo orbits. There is still a possibility, which needs further investigation, that it is a typical near-Earth asteroid that survived the aerobraking in the Earth's atmosphere and returned to a heliocentric orbit similar to that of the Earth. Based on observations made with the Southern African Large Telescope (SALT).

Kwiatkowski, T.; Kryszczy?ska, A.; Poli?ska, M.; Buckley, D. A. H.; O'Donoghue, D.; Charles, P. A.; Crause, L.; Crawford, S.; Hashimoto, Y.; Kniazev, A.; Loaring, N.; Romero Colmenero, E.; Sefako, R.; Still, M.; Vaisanen, P.

2009-03-01

240

The Orbit of Halley's Comet  

Microsoft Academic Search

RECENT investigations by Brady1 have yielded the suggestion that the historical observations of Halley's Comet can be interpreted as indicating the existence of a large planet beyond Pluto having an orbital period of 464 yr. One of us2 has carried out a detailed study of the past orbit of Halley's Comet using an extension of Cowell and Crommelin's method of

T. Kiang; P. A. Wayman

1973-01-01

241

Orbital evolution around irregular bodies  

Microsoft Academic Search

The new profiles of the space missions aimed at asteroids and comets, moving from fly-bys to rendezvous and orbiting, call for new spaceflight dynamics tools capable of propagating orbits in an accurate way around these small irregular objects. Moreover, interesting celestial mechanics and planetary science problems, requiring the same sophisticated tools, have been raised by the first images of asteroids

A. Rossi; F. Marzari; P. Farinella

1999-01-01

242

Giant Orbitals Currents in Nanostructures  

NASA Astrophysics Data System (ADS)

The possibility and origin of giant orbital currents [1] in nanostructures is investigated by model calculations. We compare two models: (i) a model where electrons are confined to a ``racetrack'' around the dot and (ii) a tight-binding model where atomic spin-orbit coupling creates macroscopic currents at the periphery of the dots. The first model yields expressions very similar to Ref. 1, but the corresponding spin-orbit coupling [2] is negligibly small, because it strongly decreases with increasing orbital radius. Furthermore, the orbital moment rapidly collapses due to a redistribution of electron with wave vectors of opposite sense of rotation. In the second model, the relatively strong intra-atomic spin-orbit interaction yields orbital currents that add [3] between neighboring atoms and create a macroscopic current at the periphery of the dot. This current corresponds to a magnetic Berry phase and cannot dissipate, because the underlying atomic orbital moments are quantized. References: [1] A. Hernando, P. Crespo, and M. A. Garc'ia, Phys. Rev. Lett. 96, 057206 (2006). [2] R. Skomski, IEEE Trans. Magn. 32, 4794 (1996). [3] J. Zhang, R. Skomski, Y. F. Lu, and D. J. Sellmyer, Phys. Rev. B 75, 214417 (2007).

Skomski, Ralph; Sellmyer, D. J.

2010-03-01

243

Multimodality imaging of the orbit  

PubMed Central

The role of imaging is well established in the evaluation of orbital diseases. Ultrasonography, Computed tomography and Magnetic resonance imaging are complementary modalities, which allow direct visualization of regional anatomy, accurate localization and help to characterize lesions to make a reliable radiological diagnosis. The purpose of this pictorial essay is to highlight the imaging features of commonly encountered pathologies which involve the orbit.

Hande, Pradipta C; Talwar, Inder

2012-01-01

244

Removing Orbital Debris with Lasers  

Microsoft Academic Search

Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the use of LEO space is threatened by runaway collisional cascading. A problem predicted more than thirty years ago, the threat from debris larger than about 1 cm demands serious attention. A promising proposed solution uses a high power pulsed laser system on the Earth to make plasma

Claude R. Phipps; Kevin L. Baker; Brian Bradford; E. Victor George; Stephen B. Libby; Duane A. Liedahl; Bogdan Marcovici; Scot S. Olivier; Lyn D. Pleasance; James P. Reilly; Alexander Rubenchik; David N. Strafford; Michael T. Valley

2011-01-01

245

Environmental dynamics at orbital altitudes  

Microsoft Academic Search

The influence of real satellite aerodynamics on the determination of upper atmospheric density was investigated. A method of analysis of satellite drag data is presented which includes the effect of satellite lift and the variation in aerodynamic properties around the orbit. The studies indicate that satellite lift may be responsible for the observed orbit precession rather than a super rotation

G. R. Karr

1976-01-01

246

The Mars Reconnaissance Orbiter Mission  

Microsoft Academic Search

The Mars Reconnaissance Orbiter (MRO) will be launched in August 2005 by an Atlas V 401 expendable launch vehicle from Cape Canaveral Air Force Station, USA. It will deliver to Mars orbit a payload to conduct remote sensing science observations, identify and characterize sites for future landers, and provide critical telecom\\/navigation relay capability for follow-on missions. The mission is designed

James E. Graf; Richard W. Zurek; Howard J. Eisen; Benhan Jai; M. D. Johnston; Ramon DePaula

2005-01-01

247

Semiclassical Quantisation Using Diffractive Orbits  

Microsoft Academic Search

Diffraction, in the context of semiclassical mechanics, describes the man- ner in which quantum mechanics smooths over discontinuities in the classical mechanics. An important example is a billiard with sharp corners; its semi- classical quantisation requires the inclusion of diffractive periodic orbits in addition to classical periodic orbits. In this paper we construct the corre- sponding zeta function and apply

N. D. Whelan

248

Pseudosymmetry analysis of molecular orbitals.  

PubMed

We introduce a pseudosymmetry analysis of molecular orbitals by means of the newly proposed irreducible representation measures. To do that we define first what we consider as molecular pseudosymmetry and the relationships of this concept with those of approximate symmetry and quasisymmetry. We develop a general algorithm to quantify the pseudosymmetry content of a given object within the framework of the finite group algebra. The obtained mathematical expressions are able to decompose molecular orbitals by means of the irreducible representations of any reference symmetry point group. The implementation and usefulness of the pseudosymmetry analysis of molecular orbitals is demonstrated in the study of ? and ? orbitals in planar and nonplanar polycyclic aromatic hydrocarbons and the t2 g and eg character of the d-orbitals in the [FeH6](3-) anion in its high spin state along the Bailar twist pathway. PMID:23436743

Casanova, David; Alemany, Pere; Falceto, Andrés; Carreras, Abel; Alvarez, Santiago

2013-02-22

249

Precision Orbit Determination for the Lunar Reconnaissance Orbiter  

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter (LRO) spacecraft was launched on June 18, 2009. In mid-September 2009, the spacecraft orbit was changed from its commissioning orbit (30 x 216 km polar) to a quasi-frozen polar orbit with an average altitude of 50km (+-15km). One of the goals of the LRO mission is to develop a new lunar reference frame to facilitate future exploration. Precision Orbit Determination is used to achieve the accuracy requirements, and to precisely geolocate the high-resolution datasets obtained by the LRO instruments. In addition to the tracking data most commonly used to determine spacecraft orbits in planetary missions (radiometric Range and Doppler), LRO benefits from two other types of orbital constraints, both enabled by the Lunar Orbiter Laser Altimeter (LOLA) instrument. The altimetric data collected as the instrument's primary purpose can be used to derive constraints on the orbit geometry at the times of laser groundtrack intersections (crossovers). The multi-beam configuration and high firing-rate of LOLA further improves the strength of these crossovers, compared to what was possible with the MOLA instrument onboard Mars Global Surveyor (MGS). Furthermore, one-way laser ranges (LR) between Earth International Laser Ranging Service (ILRS) stations and the spacecraft are made possible by the addition of a small telescope mounted on the spacecraft high-gain antenna. The photons received from Earth are transmitted to one LOLA detector by a fiber optics bundle. Thanks to the accuracy of the LOLA timing system, the precision of 5-s LR normal points is below 10cm. We present the first results of the Precision Orbit Determination (POD) of LRO through the commissioning and nominal phases of the mission. Orbit quality is discussed, and various gravity fields are evaluated with the new (independent) LRO radio tracking data. The altimetric crossovers are used as an independent data type to evaluate the quality of the orbits. The contribution of the LR data is assessed. Multi-arc solutions over entire months are presented, which allow to strengthen the LR data because fewer clock-related parameters need to be adjusted. Finally, a preliminary 1-month solution with altimetric crossover constraints is evaluated and discussed

Lemoine, F. G.; Mazarico, E.; Rowlands, D. D.; Torrence, M. H.; McGarry, J. F.; Neumann, G. A.; Mao, D.; Smith, D. E.; Zuber, M. T.

2010-05-01

250

GPS orbit processing in support of low earth orbiter precise orbit determination  

Microsoft Academic Search

There are currently an increasing number of LEO missions incorporating dual frequency GPS receivers for Satellite to Satellite Tracking. The majority of LEO precise orbit determination (POD) strategies rely on high quality GPS orbits and clocks such as those supplied by the IGS Final product. The availability of these products may not satisfy operational requirements due to their ten day

I. Romero; H. Boomkamp; J. Dow; C. Garcia

2003-01-01

251

On-Orbit-Servicing Spacecraft Flyaround Orbit Design and LQR Keep Control in Eccentric Orbits  

Microsoft Academic Search

The paper presents the initialization condition for chaser flying around target and optimal keeping control algorithm to satisfy the requirement of on-orbit-servicing in eccentric orbits. The necessary condition for chaser fly around is presented by detailed analyzing with the time variant linear relative motion formula and resolution. Then, the condition for target to locate at the center of fly around

Wang Feng; Cao Xibin; Chen Xueqin

2007-01-01

252

First ARTEMIS Spacecraft Successfully Enters Lunar Orbit  

NASA Website

The first of the two ARTEMIS spacecraft entered lunar orbit this morning. ARTEMIS was the first mission to orbit the moon's Lagrangian points and this is the first ever attempt to move from the Lagrangian into lunar orbit.

253

Semi-Active Orbital Debris Sweeper.  

National Technical Information Service (NTIS)

An orbital debris sweeper is provided for removing particles from orbit which otherwise may impact and damage an orbiting spacecraft. The debris sweeper includes a central sweeper core which carries a debris monitoring unit, and a plurality of large area ...

A. J. Petro

1990-01-01

254

Radiation therapy for orbital lymphoma  

SciTech Connect

Purpose: To describe radiation techniques and evaluate outcomes for orbital lymphoma. Methods and Materials: Forty-six patients (and 62 eyes) with orbital lymphoma treated with radiotherapy between 1987 and 2003 were included. The majority had mucosa-associated lymphoid tissue (48%) or follicular (30%) lymphoma. Seventeen patients had prior lymphoma at other sites, and 29 had primary orbital lymphoma. Median follow-up was 46 months. Results: The median dose was 30.6 Gy; one-third received <30 Gy. Electrons were used in 9 eyes with disease confined to the conjunctiva or eyelid, and photons in 53 eyes with involvement of intraorbital tissues to cover entire orbit. Local control rate was 98% for all patients and 100% for those with indolent lymphoma. Three of the 26 patients with localized primary lymphoma failed distantly, resulting in a 5-year freedom-from-distant-relapse rate of 89%. The 5-year disease-specific and overall survival rates were 95% and 88%, respectively. Late toxicity was mainly cataract formation in patients who received radiation without lens block. Conclusions A dose of 30 Gy is sufficient for indolent orbital lymphoma. Distant relapse rate in patients with localized orbital lymphoma was lower than that reported for low-grade lymphoma presenting in other sites. Orbital radiotherapy can be used for salvage of recurrent indolent lymphoma.

Zhou Ping [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)]. E-mail: pzhou@partners.org; Ng, Andrea K. [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Silver, Barbara [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Li Sigui [Department of Biostatistical Sciences, Dana-Farber Cancer Institute, Boston, MA (United States); Hua Ling [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States); Mauch, Peter M. [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)

2005-11-01

255

Computed tomography of the orbit  

SciTech Connect

In less than a decade computed tomography (CT scanning) had a profound impact on diagnostic radiology. Radiology of the orbit is no exception. As early as 1973, reports published in the radiological literature indicated that this new noninvasive imaging method was a highly effective way of demonstrating intraorbital mass lesions. As CT scanners became widely available, computed tomography became a significant adjunct to ophthalmological diagnosis. Today the main indications for CT scanning of the orbit are: (1) suspected mass lesions, most frequently presenting as exophthalmos, (2) orbital trauma, including foreign bodies, (3) some congenital anomalies, and (4) suspicion of extension into the orbit of extraorbital disease processes. Along with ultrasonography, another new noninvasive imaging technique, CT has replaced a number of more invasive and often less effective diagnostic methods, such as orbital pneumography, venography, and arteriography as major imaging techniques in orbital pathology. The paper discusses current practices in the technique of CT scanning of the orbit including the important aspect of radiation dosimetry and the clinical applications, using a number of cases to illustrate its use.

Alker, G.J.; Leslie, E.V.; Banna, M.; Pallie, W.; Rudin, S.; Bednarek, D.R.; Oh, Y.S.

1981-01-01

256

Geostationary orbit determination using SATRE  

NASA Astrophysics Data System (ADS)

A new strategy of precise orbit determination (POD) for GEO (Geostationary Earth Orbit) satellite using SATRE (SAtellite Time and Ranging Equipment) is presented. Two observation modes are proposed and different channels of the same instruments are used to construct different observation modes, one mode receiving time signals from their own station and the other mode receiving time signals from each other for two stations called pairs of combined observations. Using data from such a tracking network in China, the results for both modes are compared. The precise orbit determination for the Sino-1 satellite using the data from 6 June 2005 to 13 June 2005 has been carried out in this work. The RMS (Root-Mean-Square) of observing residuals for 3-day solutions with the former mode is better than 9.1 cm. The RMS of observing residuals for 3-day solutions with the latter mode is better than 4.8 cm, much better than the former mode. Orbital overlapping (3-day orbit solution with 1-day orbit overlap) tests show that the RMS of the orbit difference for the former mode is 0.16 m in the radial direction, 0.53 m in the along-track direction, 0.97 m in the cross-track direction and 1.12 m in the 3-dimension position and the RMS of the orbit difference for the latter mode is 0.36 m in the radial direction, 0.89 m in the along-track direction, 1.18 m in the cross-track direction and 1.52 m in the 3-dimension position, almost the same as the former mode. All the experiments indicate that a meter-level accuracy of orbit determination for geostationary satellite is achievable.

Lei, Hui; Li, Zhigang; Yang, Xuhai; Wu, Wenjun; Cheng, Xuan; Yang, Ying; Feng, Chugang

2011-09-01

257

Imaging of metastatic orbital leiomyosarcoma.  

PubMed

A 74-year-old man with a previous history of lower leg soft tissues leiomyosarcoma and multiple metastasis presented with a progressive painless proptosis of the left eye. Orbital ultrasound, CT, and MRI revealed a large mass in the left medial orbit. The mass was surgically removed and pathologic examination confirmed the diagnosis of a metastatic orbital leiomyosarcoma. The imaging characteristics of this rare tumor are comprehensively detailed, using complementary ultrasound, CT, and MRI, the combination of which allowed planning of total excision of the lesion. PMID:16304527

Voros, Gerasimos M; Birchall, Daniel; Ressiniotis, Thomas; Neoh, Christopher; Owen, Rona I; Strong, Nicholas P

2005-11-01

258

Orbital overlap and chemical bonding.  

PubMed

The chemical bonds in the diatomic molecules Li(2)-F(2) and Na(2)-Cl(2) at different bond lengths have been analyzed by the energy decomposition analysis (EDA) method using DFT calculations at the BP86/TZ2P level. The interatomic interactions are discussed in terms of quasiclassical electrostatic interactions DeltaE(elstat), Pauli repulsion DeltaE(Pauli) and attractive orbital interactions DeltaE(orb). The energy terms are compared with the orbital overlaps at different interatomic distances. The quasiclassical electrostatic interactions between two electrons occupying 1s, 2s, 2p(sigma), and 2p(pi) orbitals have been calculated and the results are analyzed and discussed. It is shown that the equilibrium distances of the covalent bonds are not determined by the maximum overlap of the sigma valence orbitals, which nearly always has its largest value at clearly shorter distances than the equilibrium bond length. The crucial interaction that prevents shorter bonds is not the loss of attractive interactions, but a sharp increase in the Pauli repulsion between electrons in valence orbitals. The attractive interactions of DeltaE(orb) and the repulsive interactions of DeltaE(Pauli) are both determined by the orbital overlap. The net effect of the two terms depends on the occupation of the valence orbitals, but the onset of attractive orbital interactions occurs at longer distances than Pauli repulsion, because overlap of occupied orbitals with vacant orbitals starts earlier than overlap between occupied orbitals. The contribution of DeltaE(elstat) in most nonpolar covalent bonds is strongly attractive. This comes from the deviation of quasiclassical electron-electron repulsion and nuclear-electron attraction from Coulomb's law for point charges. The actual strength of DeltaE(elstat) depends on the size and shape of the occupied valence orbitals. The attractive electrostatic contributions in the diatomic molecules Li(2)-F(2) come from the s and p(sigma) electrons, while the p(pi) electrons do not compensate for nuclear-nuclear repulsion. It is the interplay of the three terms DeltaE(orb), DeltaE(Pauli), and DeltaE(elstat) that determines the bond energies and equilibrium distances of covalently bonded molecules. Molecules like N(2) and O(2), which are usually considered as covalently bonded, would not be bonded without the quasiclassical attraction DeltaE(elstat). PMID:17024702

Krapp, Andreas; Bickelhaupt, F Matthias; Frenking, Gernot

2006-12-13

259

Orbit determination study results for the Venus Radar Mapper orbiter  

Microsoft Academic Search

The Venus Radar Mapper (VRM), to be launched by the U.S. in July 1988 is described and Doppler-only and Doppler plus N-Delta-VLBI data analyses are contrasted in order to evaluate the importance of VLBI data to VRM orbit determination (OD). VRM OD study results are summarized by showing the accuracy of various orbital parameters for ten cases selected over a

P. B. Esposito; S. Demcak

1986-01-01

260

Orbit determination and control for the European Student Moon Orbiter  

NASA Astrophysics Data System (ADS)

This paper presents the preliminary navigation and orbit determination analyses for the European Student Moon Orbiter. The severe constraint on the total mission ?v and the all-day piggy-back launch requirement imposed by the limited available budget, led to the choice of using a low-energy transfer, more specifically a Weak Stability Boundary one, with a capture into an elliptic orbit around the Moon. A particular navigation strategy was devised to ensure capture and fulfil the requirement for the uncontrolled orbit stability at the Moon. This paper presents a simulation of the orbit determination process, based on an extended Kalman filter, and the navigation strategy applied to the baseline transfer of the 2011-2012 window. The navigation strategy optimally allocates multiple Trajectory Correction Manoeuvres to target a so-called capture corridor. The capture corridor is defined, at each point along the transfer, by back-propagating the set of perturbed states at the Moon that provides an acceptable lifetime of the lunar orbit.

Zuiani, Federico; Gibbings, Alison; Vetrisano, Massimo; Rizzi, Francesco; Martinez, Cesar; Vasile, Massimiliano

2012-10-01

261

In-flight photometric performance of the 96Mpx focal plane array assembly for NASA's Kepler exoplanet mission  

NASA Astrophysics Data System (ADS)

Kepler is NASA's first space mission dedicated to the study of exoplanets. The primary scientific goal is statistical - to estimate the frequency of planetary systems associated with sun-like stars. Kepler was launched into an Earth-trailing heliocentric "drift-away" orbit in March 2009, and is monitoring 150,000 stars. The instrument detects the faint photometric signals of transits of those systems whose orbital planes are oriented in our line-of-sight. An Earth-Sun analog will produce a transit depth of 80 parts per million (ppm), lasting for at most a few tens of hours, and repeating once per "year". The instrumentation was designed to provide photometric data with a precision of 20 parts per million in 6.5 hours for 12th magnitude stars, resulting in a signal-to-noise ratio of 4 for an Earth-Sun transit. The stability of the flight system enables the precision of the data that reveal subtle instrumental and astrophysical effects that in turn allow a deeper understanding of the performance of the hardware, to enhanced operational procedures, and to novel post-processing of the data. The data are approaching the sensitivity needed to detect transits of terrestrial planets. Intrinsic stellar variability is now the most significant component of the photometric error budget.

Ebbets, D.; Argabright, V.; Stober, J.; Vancleve, J.; Caldwell, D.; Kolodziejczak, J.

2011-09-01

262

Optical performance of the 100-sq deg field-of-view telescope for NASA's Kepler exoplanet mission  

NASA Astrophysics Data System (ADS)

Kepler is NASA's first space mission dedicated to the study of exoplanets. The primary scientific goal is statistical - to estimate the frequency of planetary systems associated with sun-like stars, especially the detection of earth-size planets in the Habitable Zones. Kepler was launched into an Earth-trailing heliocentric "drift-away" orbit (period = 372 days) in March 2009. The instrument detects the faint photometric signals of transits of planets across the stellar disks of those systems with orbital planes fortuitously oriented in our line-of-sight. Since the probability of such alignments is small Kepler must observe a large number of stars. In fact, Kepler is monitoring approximately 150,000 stars with a 30-minute cadence. These scientific requirements led to the choice of a classical Schmidt telescope, and requirements on field-of-view (FOV), throughput, spectral bandpass, image quality, scattered light, thermal and opto-mechanical stability and in-flight adjustment authority. We review the pre-launch integration, alignment and test program, and we describe the in-flight commissioning that optimized the optical performance of the observatory. The stability of the flight system has enabled increasing recognition of small effects and increasing sophistication in data processing algorithms. Astrophysical noise arising from intrinsic stellar variability is now the dominant term in the photometric error budget.

Ebbets, D.; Atcheson, P.; Stewart, C.; Spuhler, P.; van Cleve, J.; Bryson, S.

2011-09-01

263

Asteroid searching and orbit determination  

NASA Astrophysics Data System (ADS)

This lecture reviews some basic information on asteroids relating to the ASTROD project, as well as the current progress on asteroid searching. The online resources on asteroid orbit determination are also introduced.

Zhu, Jin; Gao, Jian; Guan, Min; Yang, Bin

264

Reduced domestic satellite orbit spacing  

NASA Astrophysics Data System (ADS)

The demand for services provided by communications satellites in geostationary orbit is growing, and problems arise with respect to the required increase in capacity. One approach for providing such an increase involves the employment of more satellites operating at smaller orbital spacings. The present investigation is concerned with the results of technical studies conducted by the Federal Communications Commission (FCC) to determine the feasibility of reducing orbital spacings between U.S. 'domestic fixed satellites' (domsats). Attention is given to details regarding the usable orbital arc, an adjacent satellite interference model, antenna sidelobe patterns, a single entry analysis, a 4/6 GHz aggregate analysis, results for the 4/6 GHz bands, results for the 12/14 GHz bands, data services, voice services, video reception, and high power spot beams.

Sharp, G. L.

265

Transfer to Librations Point Orbits.  

National Technical Information Service (NTIS)

To help develop a mission analysis tool for the selection of optimum transfer orbits and launch window calculations, an analytical study of approximate admissible transfer trajectories was done to identify the domains of existence of solutions, and provid...

1986-01-01

266

Orbit IMU Alignment: Error Analysis.  

National Technical Information Service (NTIS)

A comprehensive accuracy analysis of orbit inertial measurement unit (IMU) alignments using the shuttle star trackers was completed and the results are presented. Monte Carlo techniques were used in a computer simulation of the IMU alignment hardware and ...

R. W. Corson

1980-01-01

267

Visualization of Molecular Orbitals: Formaldehyde  

ERIC Educational Resources Information Center

|Describes a computer program that plots a solid" representation of molecular orbital charge density which can be used to analyze wave functions of molecules. Illustrated with diagrams for formaldehyde. (AL)|

Olcott, Richard J.

1972-01-01

268

Real and Hybrid Atomic Orbitals.  

ERIC Educational Resources Information Center

|Demonstrates that the Schrodinger equation for the hydrogenlike atom separates in both spheroconal and prolate spheroidal coordinates and that these separations provide a sound theoretical basis for the real and hybrid atomic orbitals. (Author/SK)|

Cook, D. B.; Fowler, P. W.

1981-01-01

269

[Orbital epidermoid cyst. Case report].  

PubMed

Epidermoid tumors represent 1% of all primary intracranial tumors. Most of them occur intradurally in cerebellopontine angle and parasellar citerns. The intra-orbital location accounts for 4 to 5% of all primary intra-orbital tumors. We report the case of a 23-year-old girl with progressive right proptosis who had developed 6 months earlier. The tumor was removed via an external orbitotomy approach. Histology confirmed the diagnosis. PMID:17916370

Bertal, A; Hilmani, S; Chrifi Alaoui, S; Sami, A; Achouri, A; Ouboukhlik, A; El Kamar, A; El Azhari, A

2007-10-03

270

Low-orbit navigation concepts  

NASA Astrophysics Data System (ADS)

Low-orbit, inexpensive navigation satellite concepts applicable to civil aviation are developed as an alternative to GPS. Details are provided on orbits, signal structure, positioning software, power budget, and estimated costs and risks. Comprehensive error analysis indicates that a 2 dRMS accuracy of approxiamtely 85 m is achievable, and that the system is fault-tolerant. Rough estimates indicate that the satellite configuration will cost about $300 million.

Rome, H. James

271

Exoplanet Orbit Database (Wright+, 2011)  

NASA Astrophysics Data System (ADS)

We present a database of well determined orbital parameters of exoplanets, and their host stars' properties. This database comprises spectroscopic orbital elements measured for 427 planets orbiting 363 stars from radial velocity and transit measurements as reported in the literature. We have also compiled fundamental transit parameters, stellar parameters, and the method used for the planets discovery. This Exoplanet Orbit Database includes all planets with robust, well measured orbital parameters reported in peer-reviewed articles. The Database is available in a searcheable, filterable, and sortable form on the Web at http://exoplanets.org through the Exoplanets Data Explorer Table, and the data can be plotted and explored through the Exoplanet Data Explorer Plotter. We use the Data Explorer to generate publication-ready plots giving three examples of the signatures of exoplanet migration and dynamical evolution: We illustrate the character of the apparent correlation between mass and period in exoplanet orbits, the different selection biases between radial velocity and transit surveys, and that the multiplanet systems show a distinct semi-major axis distribution from apparently singleton systems. (2 data files).

Wright, J. T.; Kakhouri, O.; Marcy, G. W.; Han, E.; Feng, Y.; Johnson, J. A.; Howard, A. W.; Fischer, D. A.; Valenti, J. A.; Anderson, J.; Piskunov, N.

2013-01-01

272

Low Earth orbit communications satellite  

NASA Astrophysics Data System (ADS)

A current thrust in satellite communication systems considers a low-Earth orbiting constellations of satellites for continuous global coverage. Conceptual design studies have been done at the time of this design project by LORAL Aerospace Corporation under the program name GLOBALSTAR and by Motorola under their IRIDIUM program. This design project concentrates on the spacecraft design of the GLOBALSTAR low-Earth orbiting communication system. Overview information on the program was gained through the Federal Communications Commission licensing request. The GLOBALSTAR system consists of 48 operational satellites positioned in a Walker Delta pattern providing global coverage and redundancy. The operational orbit is 1389 km (750 nmi) altitude with eight planes of six satellites each. The orbital planes are spaced 45 deg., and the spacecraft are separated by 60 deg. within the plane. A Delta 2 launch vehicle is used to carry six spacecraft for orbit establishment. Once in orbit, the spacecraft will utilize code-division multiple access (spread spectrum modulation) for digital relay, voice, and radio determination satellite services (RDSS) yielding position determination with accuracy up to 200 meters.

Moroney, D.; Lashbrook, D.; McKibben, B.; Gardener, N.; Rivers, T.; Nottingham, G.; Golden, B.; Barfield, B.; Bruening, J.; Wood, D.

273

Satellite Orbital Interpolation Comparison Methods  

NASA Astrophysics Data System (ADS)

A satellite or artificial probe orbit is made of time series of orbital elements such as state vectors (position and velocities, keplerian orbital elements) given at regular or irregular time intervals. These time series are fitted to observations, so that differences between observations (distance, radial velocity) and the theoretical quantity be minimal, according to a statistical criterion, mostly based on the least-squared algorithm. These computations are carried out using dedicated software, such as the GINS used by GRGS, mainly at CNES Toulouse and Paris Observatory. From an operational point of view, time series of orbital elements are 7-day long. Depending on the dynamical configurations, more generally, they can typically vary from a couple of days to some weeks. One of the fundamental parameters to be adjusted is the initial state vector. This can lead to time gaps, at the level of a few dozen of centimeters between the last point of a time series to the first one of the following data set. The objective of this presentation consists in the improvement of an interpolation method freed itself of such possible "discontinuities" resulting between satellite's orbit arcs when a new initial bulletin is adjusted. We show the principles of interpolation for these time series and compare solutions coming from different interpolation methods such as Lagrange polynomial, spline cubic, Chebyshev orthogonal polynomial and cubic Hermite polynomial. These polynomial coefficients are used to reconstruct and interpolate the satellite orbits without time gaps and discontinuities and requiring a weak memory size.

Richard, J.-Y.; Deleflie, F.; Gambis, D.

2012-04-01

274

Precision Orbit Determination for the Lunar Reconnaissance Orbiter  

NASA Astrophysics Data System (ADS)

The U.S. Lunar Reconnaissance Orbiter (LRO) mission will be launched in October 2008, and will carry out a detailed mapping of the Moon using a science payload of multiple instruments, including the Lunar Orbiter Laser Altimeter (LOLA), and the Lunar Reconnaissance Orbiter Camera (LROC) (Chin, 2007). One of the primary goals of the LRO mission is develop a geodetic grid for the planet. A subsidiary goal is the improvement of the lunar gravity field. The environment for POD on LRO is especially challenging. The spacecraft will orbit the Moon at a mean altitude of 50 km, and the expected error from the Lunar Prospector series of gravity models (to degree 100 or to degree 150) can be expected to be hundreds of meters. LRO will be tracked by S Band Doppler from White Sands, New Mexico, and Dongara, Australia, as well as by one-way laser ranging from Satellite Laser Ranging (SLR) tracking stations on the Earth. However, unlike the Japanese lunar mission SELENE (Kaguya), no direct tracking will be available while the spacecraft is over the lunar farside. We review the status of orbit modelling for LRO, for both the geopotential modelling and the nonconservative force models, as well as anticipated improvements. We discuss the modelling for the one-way laser ranging observable, and how the data from the one-way laser ranging (LR) system will be acquired from selected stations of the global stations of the SLR network. We discuss the orbit determination strategies which we expect to implement on this mission, including the use of altimeter crossovers from the LOLA instrument to supplement the Earth-based tracking and we review the projected orbit determination accuracies that will be attainable.

Lemoine, Frank; Rowlands, David; McGarry, Jan; Neumann, Gregory; Chinn, Douglas; Mazarico, Erwan; Torrence, Mark

275

Space Tourism: Orbital Debris Considerations  

NASA Astrophysics Data System (ADS)

Space activities after a phase of research and development, political competition and national prestige have entered an era of real commercialization. Remote sensing, earth observation, and communication are among the areas in which this growing industry is facing competition and declining government money. A project like International Space Station, which draws from public money, has not only opened a window of real multinational cooperation, but also changed space travel from a mere fantasy into a real world activity. Besides research activities for sending man to moon and Mars and other outer planets, space travel has attracted a considerable attention in recent years in the form of space tourism. Four countries from space fairing nations are actively involved in the development of space tourism. Even, nations which are either in early stages of space technology development or just beginning their space activities, have high ambitions in this area. This is worth noting considering their limited resources. At present, trips to space are available, but limited and expensive. To move beyond this point to generally available trips to orbit and week long stays in LEO, in orbital hotels, some of the required basic transportations, living requirements, and technological developments required for long stay in orbit are already underway. For tourism to develop to a real everyday business, not only the price has to come down to meaningful levels, but also safety considerations should be fully developed to attract travelers' trust. A serious hazard to space activities in general and space tourism in particular is space debris in earth orbit. Orbiting debris are man-made objects left over by space operations, hazardous to space missions. Since the higher density of debris population occurs in low earth orbit, which is also the same orbit of interest to space tourism, a careful attention should be paid to the effect of debris on tourism activities. In this study, after a review of the current work on space tourism and debris situation in low earth orbit suitable orbits for space tourism activities with regard to the presence of orbital debris are discussed.

Mahmoudian, N.; Shajiee, S.; Moghani, T.; Bahrami, M.

2002-01-01

276

THE ORBITS OF THE OUTER URANIAN SATELLITES  

SciTech Connect

We report on the numerically integrated orbits for the nine outer Uranian satellites. The orbits are calculated based on fits to the astrometric observations for the period from 1984 to 2006. The results include the state vectors, post-fit residuals, and mean orbital elements. We also assess the accuracy of the orbital fits and discuss the need for future measurements.

Brozovic, M.; Jacobson, R. A. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 (United States)], E-mail: marina.brozovic@jpl.nasa.gov

2009-04-15

277

Optimal parking orbits for manned Mars missions  

Microsoft Academic Search

This paper summarizes a Mars parking orbit optimization effort. This parking orbit study includes the selection of optimal elliptic Mars parking orbits that meet mission constraints and that include pertinent apsidal misalignment losses. Mars missions examined are for the opportunity years of 2014, 2016, and 2018. For these mission opportunities, it is shown that the optimal parking orbits depend on

Michael L. Cupples; Jill A. Nordwall

1993-01-01

278

Orbits Around Black Holes in Triaxial Nuclei  

Microsoft Academic Search

We discuss the properties of orbits within the influence sphere of a supermassive black hole (BH), in the case that the surrounding star cluster is non-axisymmetric. There are four major orbit families; one of these, the pyramid orbits, have the interesting property that they can approach arbitrarily closely to the BH. We derive the orbit-averaged equations of motion and show

David Merritt; Eugene Vasiliev

2011-01-01

279

Elements of a Chemical Orbital Theory  

NASA Astrophysics Data System (ADS)

Interaction is important in chemistry. Interactions of atoms form chemical bonds. Bonds interact with each other in molecules to determine the molecular properties. Interactions of molecules give rise to chemical reactions. Electrons control atoms, bonds, and molecules. The behavior of electrons is simply and effectively represented by orbitals, which contain wave properties, i.e., phase and amplitude. In our chemical orbital theory we consider the interactions of the orbitals of atoms, bonds and molecules. The elements of the chemical orbital theory are separated into three groups: (1) interactions of two orbitals, (2) interactions of three orbitals, and (3) cyclic interactions of more than two orbitals. Here, general aspects of the interactions of two orbitals are summarized to show the background of this volume and assist nonspecialists to read the following chapters. Among the keywords are: phase and amplitude of orbitals, strength of orbital interactions, electron delocalization, electron localization, exchange repulsion, ionization energy, electronic spectrum, frontier orbitals, reactivity, selectivity, orbital symmetry, and so on. The remaining elements of the chemical orbital theory, i.e., an orbital mixing rule for the three-orbital interactions and an orbital phase theory for the cyclic interactions, are introduced briefly.

Inagaki, Satoshi

280

Atomic Electron Populations by Molecular Orbital Theory.  

National Technical Information Service (NTIS)

The detailed distribution of electrons in molecules can be broken down into atomic orbital populations if an atomic orbital basis is used for a molecular orbital wave function (LCAO). A total assignment of all electrons in a molecule to atomic orbitals (a...

W. J. Hehre R. F. Stewart J. A. Pople

1968-01-01

281

Mars Reconnaissance Orbiter Accelerometer Experiment Results  

Microsoft Academic Search

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005, designed for aerobraking, achieved Mars Orbital Insertion (MOI), March 10, 2006. Atmospheric density decreases exponentially with increasing height. By small propulsive adjustments of the apoapsis orbital velocity, periapsis altitude is fine tuned to the density surface that safely used the atmosphere of Mars to aerobrake over 400 orbits. MRO periapsis

G. M. Keating; S. W. Bougher; M. E. Theriot; R. W. Zurek; R. C. Blanchard; R. H. Tolson; J. R. Murphy

2007-01-01

282

Poynting-Robertson drag and orbital resonance  

Microsoft Academic Search

Both the Poynting-Robertson drag and resonant orbits appear to be very important for the motion of small grains in the early solar system. While orbital resonances are very often stable and tend to force bodies into noncircular orbits, the Poynting-Robertson drag produces secular variations in the semimajor axis and tends to circularize the orbits. This paper presents a numerical study

R. Gonczi; Ch. Froeschle; C. Froeschle

1982-01-01

283

The superior orbital fissure and its contents  

Microsoft Academic Search

Topographic landmarks for the superior orbital fissure are useful for general orientation and approach to the middle fossa, cavernous sinus and orbit. In this study, the microsurgical anatomy and morphometry of the superior orbital fissure and its related structures were examined in 57 disarticulated sphenoid bones, 102 skull bases and 58 adult cadaveric heads. The superior orbital fissure was observed

F. Govsa; G. Kayalioglu; M. Erturk; T. Ozgur

1999-01-01

284

Osseous Anatomy of the Orbital Apex  

Microsoft Academic Search

The osseous anatomy of the orbital apex may be difficult to conceptualize because of the dif- ferent shapes and orientations of the optic ca- nal, superior and inferior orbital fissures, and foramen rotundum. However, knowing this anatomy is crucial to evaluate complex frac- tures, tumors, and inflammatory processes in- volving the orbital apex. Evaluating osseous anatomy of the orbital apex

David L. Daniels; Leighton P. Mark; Mahmood F. Mafee; Bruce Massaro; Lloyd E. Hendrix; Katherine A. Shaffer; David Morrissey; Charles W. Horner

285

The superior orbital fissure and its contents  

Microsoft Academic Search

Summary Topographic landmarks for the superior orbital fissure are useful for general orientation and approach to the middle fossa, cavernous sinus and orbit. In this study, the microsurgical anatomy and morphometry of the superior orbital fissure and its related structures were examined in 57 disarticulated sphenoid bones, 102 skull bases and 58 adult cadaveric heads. The superior orbital fissure was

F. Govsa; G. Kayalioglu; M. Erturk; T. Ozgur

1999-01-01

286

Orbital manifestations of Noonan syndrome.  

PubMed

Noonan syndrome describes a rare multisystem condition that manifests with Turner syndrome phenotype combined with numerous systemic and facial characteristics. The most common systemic findings include cardiac defects, short stature, chest deformity, hearing loss, and bleeding diatheses. Patients with Noonan syndrome are also at a greater risk of developing various types of malignancies. Facial characteristics of Noonan syndrome consist of broad forehead, low-set ears, short and webbed neck, and low hairline. External ocular findings include hypertelorism, ptosis, epicanthal folds, antimongoloid slant, downward-sloping palpebral fissures, and malar flattening. In this case series and review of the literature, the authors present 2 cases of Noonan syndrome that embody the diverse spectrum of orbital manifestations associated with this rare disorder. The first case demonstrates more profound orbital pathology, including bilateral orbital giant cell reparative granulomas, proptosis, hypertelorism, shallow orbits, upper eyelid ptosis, and lower eyelid retraction. The second case displays classic Turner-syndrome-like facial characteristics including a broad forehead with low hairline, low-set ears, and short and webbed neck. Orbital findings were subtle and consisted of bilateral lower eyelid retraction and shallow orbits. In conclusion, Noonan syndrome is a rare congenital disorder with a wide spectrum of clinical findings. Various intraorbital and extraorbital tumors may occur in patients with Noonan syndrome, with giant cell reparative granuloma being the most commonly encountered. In patients with orbital tumors and eyelid retraction, the authors describe successful treatment through decompression, tumor extraction, and lower eyelid retractor release. Patients who present with ocular irritation and exposure due to less severe lower eyelid malposition may be successfully treated with lower eyelid retraction repair combined with lateral internal tarsoconjunctival tarsorrhaphy. PMID:21464791

Randolph, John C; Sokol, Jason A; Lee, Hui Bae H; Nunery, William R

287

Orbit Evolution in Common Envelopes  

NASA Astrophysics Data System (ADS)

We study how the inclination angle and eccentricity evolve during a common envelope phase. During a common envelope phase, a compact star is swallowed by its giant companion and spirals into a tighter orbit. A close binary results if the compact star releases enough energy to expel the envelope. We investigate possible fossil evidence of the common envelope phase on the inclination angle and the eccentricity. A convective common envelope leads to force component perpendicular to the orbital plane, and thus change the orbital inclination. This makes it harder to uniquely identify the signature of neutron star natal kicks. A common envelope is usually assumed to circularize orbits, but some eccentricity in fact arises both from the spiral-in process itself, and from random forces in the orbital plane. When the envelope is expelled, it might seem that the binary system would preserve whatever eccentricity had been established at the final stage of the inspiral. But tidal dissipation by the residual envelope can reduce the eccentricity. The final eccentricity depends on which of these effects wins or how they balance each other. We discuss applications and observational tests of these predictions.

Luan, Jing; Phinney, E. S.

2011-09-01

288

Orbital Metastasis of Breast Carcinoma  

PubMed Central

We report a case of orbital metastasis in a previously diagnosed metastatic breast cancer in a 46-year old woman presenting with diplopia and proptosis of her left eye bulb. An orbital computed-tomography (CT) and a magnetic resonance imaging (MRI) both revealed an intra-orbital extra-bulbar mass of 1.5 × 3 cm in size, in the left orbit. The patient had been diagnosed with stage IV breast cancer 4 years before. She had received chemotherapy with docetaxel and was on hormone therapy at the time of presentation of her eye symptoms. Current treatment included systemic combination therapy with docetaxel and capecitabine as well as local irradiation with stereotactic radiosurgery (cyberknife). There was a gradual improvement of local symptoms and signs. The metastatic involvement of the orbit in malignant tumors is a rarely diagnosed condition. Breast cancer accounts for the majority of these cases. The appearance of eye symptoms in patients with a history of cancer should always be investigated with a consideration of ocular metastatic disease.

Vlachostergios, Panagiotis J.; Voutsadakis, Ioannis A.; Papandreou, Christos N.

2009-01-01

289

Anterior Orbit and Adnexal Amyloidosis  

PubMed Central

Purpose: To describe six cases of anterior orbital and adnexal amyloidosis and to report on proteomic analysis to characterize the nature of amyloid in archived biopsies in two cases. Materials and Methods: The clinical features, radiological findings, pathology, and outcome of six patients with anterior orbit and adnexal amyloidosis were retrieved from the medical records. The biochemical nature of the amyloid was determined using liquid chromatography/mass spectroscopy archived paraffin-embedded tissue in two cases. Results: Of the six cases, three had unilateral localized anterior orbit and lacrimal gland involvement. Four of the six patients were female with an average duration of 12.8 years from the time of onset to presentation eyelid infiltration by amyloid caused ptosis in five cases. CT scan in patients with lacrimal gland involvement (n = 3) demonstrated calcified deformable anterior orbital masses and on pathological exmaintionamyloid and calcific deposits replaced the lacrimal gland acini. Ptosis repair was performed in three patients with good outcomes. One patient required repeated debulking of the mass and one patient had recurrenct disease. Proteomic analysis revealed polyclonal IgG-associated amyloid deposition in one patient and AL kappa amyloid in the second patient. Conclusion: Amyloidosis of the anterior orbit and lacrimal gland can present with a wide spectrum of findings with good outcomes after surgical excision. The nature of amyloid material can be precisely determined in archival pathology blocks using diagnostic proteomic analysis.

Al Hussain, Hailah; Edward, Deepak P.

2013-01-01

290

Orbital, Rotational, and Climatic Interactions  

SciTech Connect

The report of an international meeting on the topic of Orbital, Rotational, and Climatic Interactions, which was held 9-11 Jul. 1991 at the Johns Hopkins University is presented. The meeting was attended by 22 researchers working on various aspects of orbital and rotational dynamics, paleoclimate data analysis and modeling, solid-Earth deformation studies, and paleomagnetic analyses. The primary objective of the workshop was to arrive at a better understanding of the interactions between the orbital, rotational, and climatic variations of the Earth. This report contains a brief introduction and 14 contributed papers which cover most of the topics discussed at the meeting. Separate abstracts have been prepared for articles from this report.

Bills, B.G.

1992-12-01

291

Multiple Myeloma of the Orbit  

PubMed Central

The authors report a case of a 62-year-old female with history of multiple myeloma who presents with complains of swelling and pain in her right eye. On examination, it was found that she has proptosis, chemosis, and diplopia along with decreased vision. Initial workup and treatment did not yield significant results, eventually she was found to have myelomatous changes in her right orbit on MRI and was diagnosed with multiple myeloma of the orbit which resolved solely with radiation. This case tends to highlight the importance of considering myeloma of the orbit as a very important and early differential diagnosis in a patient with a history of multiple myeloma presenting with a swollen and painful eye.

Hassan, Mona; Alirhayim, Zaid; Sroujieh, Laila; Hassan, Syed

2012-01-01

292

Observation of molecular orbital gating.  

PubMed

The control of charge transport in an active electronic device depends intimately on the modulation of the internal charge density by an external node. For example, a field-effect transistor relies on the gated electrostatic modulation of the channel charge produced by changing the relative position of the conduction and valence bands with respect to the electrodes. In molecular-scale devices, a longstanding challenge has been to create a true three-terminal device that operates in this manner (that is, by modifying orbital energy). Here we report the observation of such a solid-state molecular device, in which transport current is directly modulated by an external gate voltage. Resonance-enhanced coupling to the nearest molecular orbital is revealed by electron tunnelling spectroscopy, demonstrating direct molecular orbital gating in an electronic device. Our findings demonstrate that true molecular transistors can be created, and so enhance the prospects for molecularly engineered electronic devices. PMID:20033044

Song, Hyunwook; Kim, Youngsang; Jang, Yun Hee; Jeong, Heejun; Reed, Mark A; Lee, Takhee

2009-12-24

293

Odontogenic myxoma with orbital involvement.  

PubMed

A 15-month-old female child presented with progressive right-sided facial swelling, nasal obstruction, and deviation of the nose to the left. Computed tomography revealed a cystic mass in the maxillary sinus with disruption of the medial orbital floor. Incisional biopsy of this mass was nondiagnostic and the mass continued to grow rapidly. The mass was removed by excisional biopsy and curettage with conservative margins via combined lateral rhinotomy and sublabial approaches. Intraoperatively, a large defect of the floor that extended to the orbital apex was noted. Histopathology revealed an odontogenic myxoma. Odontogenic myxomas are uncommon tumors that are usually seen in adults. Our case is unique because to the best of our knowledge, it is the first reported case with orbital involvement in the pediatric population. PMID:23034692

Chen, Henry H; Streubel, Sven-Olrik; Durairaj, Vikram D

294

Energy and the Elliptical Orbit  

NASA Astrophysics Data System (ADS)

In the January 2007 issue of The Physics Teacher, Prentis, Fulton, Hesse, and Mazzino1 describe a laboratory exercise in which students use a geometrical analysis inspired by Newton to show that an elliptical orbit and an inverse-square law force go hand in hand. The historical, geometrical, and teamwork aspects of the exercise are useful and important. This paper presents an exercise which uses an energy/angular momentum conservation model for elliptical orbits. This exercise can be done easily by an individual student and on regular notebook-sized paper.

Nettles, Bill

2009-03-01

295

Constraints on Triton's Orbital Evolution  

NASA Astrophysics Data System (ADS)

Three models have been proposed for the capture origin of Triton: Collision with a preexisting satellite (Goldreich 1989), Gas drag (McKinnon 1990), and three-body exchange (Agnor and Hamilton 2004). All three scenarios put Triton onto a highly elongated orbit which is subsequently circularized by satellite tides. Our goal here is to use the current state of the Neptunian system to constrain these capture scenarios. Triton strongly affects inner satellites (or an inner disk) directly via close pericenter passages before its orbit circularizes. Since satellite tides nearly conserve angular momentum, a simple tidal model puts Triton's minimum pericenter distance at aT/2 ˜ 7RN, where aT is its current semimajor axis. Our initial simulations show that some satellites orbiting outside Proteus (the outermost of the inner satellites at a=4.67RN) can survive these Triton passages. So why are there no known moonlets beyond 4.67RN? Seeking answers, we have integrated Triton's orbit backwards in time with a more sophisticated model that includes J2, solar perturbations, and satellite tides. We find that Triton's pericenter smoothly descends toward 7RN, as in the simple tidal model, but with superimposed oscillations at i) 1/2 Neptune's orbital period and ii) the nodal and apsidal precession periods. At a ˜ 94RN Triton encounters a Kozai-like resonance between these precession periods which causes its pericenter to dip to ˜ 4.2RN - well within the current orbit of Proteus. If Triton's orbit were ever this large, then the early inner satellite system must have been much smaller than it is today. Additional apsidal and nodal resonances between an early Triton on a highly elliptical orbit and the small inner satellites (with resonant arguments like 2nT - 2? sat) are strong enough to drive moonlet inclinations up to several degrees. We are using the stengths and locations of these resonances to further limit possible capture and evolution scenarios and will report on the status of these investigations.

Hamilton, D. P.; Zhang, K.; Agnor, C.

2005-05-01

296

Orbital Maneuvering Vehicle - New capability  

NASA Astrophysics Data System (ADS)

The Orbital Maneuvering Vehicle (OMV) program is reviewed with reference to the current status of the program, vehicle description, and mission capabilities. The OMV, which will be available in 1991, will be able to economically deliver and retreive spacecraft from orbits beyond the practical limits of the Shuttle. It will be capable of meeting the present needs of the Space Transportation System and its payloads and the future space activities associated with the Space Station. In addition to the inherent capability of the OMV, it can be enhanced by the addition of special purpose mission kits to meet special mission needs, such as servicing, refueling, and recovery of tumbling satellites.

Huber, William G.

1987-10-01

297

Extraskeletal Osteosarcoma of the Orbit  

PubMed Central

Patient. We report a 22-year-old male presenting with extraskeletal osteosarcoma of the orbit. Discussion. Extra skeletal osteosarcomas are uncommon tumours, usually arising from the lower extremities or girdle. These are aggressive tumours with high metastatic potential and poor outcome. Optimal treatment is undefined, and the role of radical surgery, radiotherapy and aggressive chemotherapy is currently being evaluated. The orbit is a rare site for extraskeletal osteosarcoma, with the only previous case reported in an 11-year-old male, who was irradiated in infancy for a retinoblastoma.

Abraham, Elizabeth; Jyothirmayi, Rema; Nair, Madhavan Krishnan

1998-01-01

298

Orbits of 15 visual binaries  

NASA Astrophysics Data System (ADS)

Micrometer observations in 1979-1980 permitted the computation of substantially revised or new orbital elements for 15 visual pairs. They include the bright stars 52 Ari and 78 UMa (in the UMa cluster), four faint dK pairs, and the probable triple ADS 16185. Ephemerides for equator of data are listed in a table along with the orbital elements of the binaries. The measured positions and their residuals are listed in a second table. The considered binaries include ADS 896, 2336, 6315, 7054, 7629, 8092, 8555, 8739, 13987, 16185, Rst 1658, 3906, 3972, 4529, and Jsp 691.

Heintz, W. D.

1981-04-01

299

Orbital effects in actinide systems  

SciTech Connect

Actinide magnetism presents a number of important challenges; in particular, the proximity of 5f band to the Fermi energy gives rise to strong interaction with both d and s like conduction electrons, and the extended nature of the 5f electrons means that they can interact with electron orbitals from neighboring atoms. Theory has recently addressed these problems. Often neglected, however, is the overwhelming evidence for large orbital contributions to the magnetic properties of actinides. Some experimental evidence for these effects are presented briefly in this paper. They point, clearly incorrectly, to a very localized picture for the 5f electrons. This dichotomy only enhances the nature of the challenge.

Lander, G.H.

1983-01-01

300

Magnetorquer Control for Orbital Manoeuvre of Low Earth Orbit Microsatellite  

Microsoft Academic Search

A propulsion system is required in order for the spacecraft to be able to operate as a part of the constellation, and is used to carry out initial launcher injection corrections, spacecraft separation into their respective orbital slots, altitude maintenance and finally an end of life manoeuvre to remove the spacecraft from the operational system also these manoeuvres allow the

A. M. SI MOHAMMED; A. BOUDJEMAI; S. CHOURAQUI; M. BENYETTOU

301

BINARY STAR ORBITS. IV. ORBITS OF 18 SOUTHERN INTERFEROMETRIC PAIRS  

SciTech Connect

First orbits are presented for 3 interferometric pairs and revised solutions for 15 others, based in part on first results from a recently initiated program of speckle interferometric observations of neglected southern binaries. Eight of these systems contain additional components, with multiplicity ranging up to 6.

Mason, Brian D.; Hartkopf, William I. [U.S. Naval Observatory, 3450 Massachusetts Avenue, NW, Washington, DC 20392-5420 (United States); Tokovinin, Andrei, E-mail: bdm@usno.navy.mi, E-mail: wih@usno.navy.mi, E-mail: atokovinin@ctio.noao.ed [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile)

2010-09-15

302

Independent Orbiter Assessment (IOA): Analysis of the Orbital Maneuvering System.  

National Technical Information Service (NTIS)

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, an...

C. D. Prust D. J. Paul V. J. Burkemper

1987-01-01

303

Getting a Crew into Orbit  

ERIC Educational Resources Information Center

|Despite the temporary setback in our country's crewed space exploration program, there will continue to be missions requiring crews to orbit Earth and beyond. Under the NASA Authorization Act of 2010, NASA should have its own heavy launch rocket and crew vehicle developed by 2016. Private companies will continue to explore space, as well. At the…

Riddle, Bob

2011-01-01

304

Thrust aided sub-orbits  

Microsoft Academic Search

A discussion on thrust assisted sub-orbits is presented. This operation may be considered as a candidate means for providing station-keeping, for the interrogation of circulating satellites, and as an operational maneuver for pick-up, launch and\\/or inspection of experiment modules (and the like) from (say) the SHUTTLE spacecraft.

J. B. Eades

1977-01-01

305

Comet Odyssey: Comet Nucleus Orbiter  

Microsoft Academic Search

Comet Odyssey is a comet nucleus orbiter mission, proposed to NASA's Discovery program in 2004. The goal of the mission is to completely characterize a cometary nucleus, both physically and compositionally, as can only be done during an extended rendezvous and not with a fast flyby. Comet Odyssey will launch in October 2009 on a Delta II 7925 and use

P. R. Weissman; W. D. Smythe; S. J. Spitz; D. E. Bernard; R. W. Bailey

2004-01-01

306

Variational definitions of orbital energies  

NASA Astrophysics Data System (ADS)

A formulation of Koopmans' theorem is derived for high-spin half-filled open shells in the restricted openshell Hartree-Fock (ROHF) method based on a variational treatment of both the initial (non-ionized) open-shell system X with spin S and the corresponding ions having a hole or an extra electron in the closed, open and virtual shells respectively. The six processes for forming ions with spin S+/-1/2 require two different definitions for canonical orbitals within each shell. These processes may be treated equivalently within a restricted CI using arbitrary non-canonical linear transforms of the ROHF orbitals optimal for the initial system. Canonical UHF orbitals also obey a variational principle for the ion energies, but they provide less appropriate estimates for actual states of the ion. Canonical spin-unrestricted Kohn-Sham orbitals with common exchange-correlation functionals suffer from all of the UHF problems and from selfinteraction error. They generally are not useful estimates for ion energies.

Davidson, Ernest R.

2012-12-01

307

Gravitational Orbits and Space Flight  

NSDL National Science Digital Library

These lecture notes discuss Newton's theories of dynamics and gravity. The various kinds of possible orbits are described in this lecture. The evolution of space technology such as rockets, the Space Shuttle, dozens of robot spacecraft, and the human space program are also discussed.

O'Connell, Robert

2005-06-28

308

The orbit of (2) Pallas.  

NASA Astrophysics Data System (ADS)

A comparison between recent astrometric observations of the asteroid (2) Pallas made at Bordeaux Observatory with the positions given in the Ephemerides of Minor Planets (EMP) published by the Institute of Theoretical Astronomy at St Petersburg shows systematic offsets in right ascension, about 0.6". The orbital elements of Pallas given in the EMP since 1986 are based on a set of orbital elements of Pallas published in 1984 on Minor Planet Circular (MPC) 8665. We give in this paper some arguments which prove that the offsets between the observed and the calculated positions can be explained as follows: the orbital elements of Pallas given on MPC 8665 were considered to be expressed in the usual (FK4, B1950.0) system when introduced in the EMP for 1986, whereas we prove that they are expressed in the non-standard (FK5, B1950.0) system. We then make a new determination of the orbital elements of Pallas directly in the (FK5, J2000.0) system, and of the mass of (1) Ceres, adding to the data found in Landgraf (1987) and covering the period 1802-1978, the positions obtained with the Bordeaux and La Palma automatic meridian circles from 1984 to 1993. The result obtained for the mass of Ceres is (5.0+/-0.2)10^-10^ solar masses, which is in agreement with the average of the values obtained by other authors.

Viateau, B.; Rapaport, M.

1995-06-01

309

Sildenafil for pediatric orbital lymphangioma.  

PubMed

IMPORTANCE Orbital lymphangiomas, congenital hamartomas of the lymphovascular tissue, are often associated with significant ocular complications and can be challenging to treat. To date, therapeutic approaches have demonstrated variable results and have significant ocular and systemic risks. We present 2 cases of pediatric orbital lymphangioma that responded to treatment with oral sildenafil. OBSERVATIONS This is a report of a series of 2 patients at the University of California-Davis Medical Center treated between March 2011 and October 2012. The first patient was a 12-month-old male infant whose extensive orbital and facial lymphangioma responded to sildenafil after repeated sclerosing and drainage procedures failed to achieve remission. The second patient was a 12-year-old boy whose orbital lymphangioma and associated ocular pain improved with sildenafil, making enucleation unnecessary. CONCLUSIONS AND RELEVANCE These reported cases demonstrate promise for sildenafil as a noninvasive therapy for pediatric lymphangioma. Larger clinical trials are needed to clarify the optimal length of treatment, use as monotherapy, and long-term adverse effects. PMID:23828510

Gandhi, Nandini G; Lin, Lily Koo; O'Hara, Mary

2013-09-01

310

Orbital lifetime of tethered satellites  

Microsoft Academic Search

Two models of an uncontrolled tethered system comprised of a free tether, a satellite trailing a tether, or two end bodies tethered together are developed to study the orbital lifetime characteristics of such systems. The first, a lumped mass model, including an extensible, nonconductive tether connecting end bodies modeled as spheres, is used as a 'truth' model. The second, a

Ted W. Warnock; John E. Cochran Jr.

1992-01-01

311

Energy and the Elliptical Orbit  

ERIC Educational Resources Information Center

In the January 2007 issue of "The Physics Teacher," Prentis, Fulton, Hesse, and Mazzino describe a laboratory exercise in which students use a geometrical analysis inspired by Newton to show that an elliptical orbit and an inverse-square law force go hand in hand. The historical, geometrical, and teamwork aspects of the exercise are useful and…

Nettles, Bill

2009-01-01

312

Energy and the Elliptical Orbit  

ERIC Educational Resources Information Center

|In the January 2007 issue of "The Physics Teacher," Prentis, Fulton, Hesse, and Mazzino describe a laboratory exercise in which students use a geometrical analysis inspired by Newton to show that an elliptical orbit and an inverse-square law force go hand in hand. The historical, geometrical, and teamwork aspects of the exercise are useful and…

Nettles, Bill

2009-01-01

313

The Transfer Orbit Stage program  

NASA Astrophysics Data System (ADS)

The current status of the Transfer Orbit Stage (TOS) program aimed at the manufacturing of a new space transfer vehicle compatible with the Space Transportation System, is reviewed. The discussion includes the principal stages of the TOS program, the main features of the approach to the program, the requirements for the TOS system, the general system design, system operations, ground support, and mission applications.

Thompson, David W.

1987-10-01

314

Orbits in Strongly Curved Spacetime  

NSDL National Science Digital Library

This applet shows from three different physical perspectives the orbit of a low-mass test particle around a non-rotating black hole. Below the applet is an instructional guide to the applet and a description of the parameters involved.

Walker, John

2005-02-11

315

Non-infectious orbital vasculitides  

PubMed Central

Non-infectious vasculitides comprise a large number of diseases. Many of these diseases can cause inflammation within the orbit and a clinical presentation, which mimics numerous other processes. Orbital disease can often be the initial presentation of a systemic process and early diagnosis can help prevent long-term, potentially fatal consequences. The evaluation and treatment of non-infectious orbital vasculitides are often complicated and require a thorough understanding of the disease and underlying systemic associations. The long-term prognosis visually and systemically must be weighed against the risks and benefits of the treatment regimen. A large variety of corticosteroid formulations currently exist and are the mainstay of initial treatment. Traditional steroid-sparing immunosuppressive agents are also an important arsenal against these vasculitides. Recently, a new class of drugs called biologics, which target the various mediators of the inflammation cascade, may potentially provide more effective and less toxic treatment. This review aims to synthesize the current literature on non-infectious orbital vasculitides.

Perumal, B; Black, E H; Levin, F; Servat, J J

2012-01-01

316

Orbit Determination from the Satellite.  

National Technical Information Service (NTIS)

The paper presents simple methods for determining moderately eccentric orbits from the satellite; linear combinations of time-of-flight measurements are used exclusively. The method is based on a third-order expansion of the satellite law of motion in ter...

A. Braga-Illa

1968-01-01

317

Orbit Determination from Minitrack Observations.  

National Technical Information Service (NTIS)

Although Minitrack observations are only accurate to about 1 minute of arc, accurate orbits have been obtained for a number of satellites. This is due to the excellent global coverage of the NASA Minitrack network. The accuracy obtained for eccentricity i...

R. H. Gooding

1966-01-01

318

Error Derivatives for Elliptic Orbits.  

National Technical Information Service (NTIS)

When an increment of velocity is applied to an orbiting vehicle in an attempt to bring it to earth, errors will exist in the assumed position and velocity of the vehicle and in the applied velocity increment. If these errors are sufficiently small, a line...

E. R. Lancaster

1964-01-01

319

Autonomous rendezvous in elliptical orbits  

Microsoft Academic Search

An important feature of the autonomous terminal rendezvous of spacecraft in an elliptical orbit is a periodic motion (limit cycle) in the system variables. Unstable limit cycle involves an instability of the system. This paper addresses a mathematical model of the system, a range rate control algorithm, a numerical iterative method for computing the limit cycle, its stability and domain

Y. Shaohua

1997-01-01

320

Short-Arc Correlation and Initial Orbit Determination For Space-Based Observations  

NASA Astrophysics Data System (ADS)

Initial orbit determination (IOD) of space debris is an important segment of space situational awareness and is often coupled with the problem of track correlation, since in order to determine the orbit of an observed object, multiple observations must be combined. It is generally uncertain, however, whether two arbitrary tracks are of the same object. Recently, Fujimoto and Scheeres have proposed a novel and rigorous track correlation and IOD technique where each observation is assigned an “admissible region” in state space based on some physical constraints. The relationship of two observations is then determined by finding whether these regions intersect via Bayes’ rule. In this paper, we propose a new application of this method to space-based observations. Preliminary results show robustness to classically singular geometries, such as GEO-on-GEO observations. Admissible regions were first proposed by Milani et al. for heliocentric orbits, and Tommei et al. expanded this concept to Earth orbiting objects. Maruskin et al. was first to introduce the concept of intersecting multiple admissible regions to correlate tracks and obtain an initial orbit estimate, albeit the correlation was conducted in 2-dimensional subspaces of the state space. Fujimoto and Scheeres fully developed ways of characterizing intersections of admissible regions in the full 6-dimensional state space. They showed through topological arguments that a positive correlation also simultaneously provides an initial orbit estimate. A method of linearly mapping admissible regions to the state space was introduced in order to improve computational turn-around, and was validated with a series of numerical tests. For space-based observations, the observation location vector, previously assumed to be Earth-fixed, is now allowed to propagate under two-body dynamics. Several technical challenges arise when we make this change. First, the admissible region spans over a larger region in the state space, making the correlation process more computationally intensive. Second, a modification must be made to the correlation process as the observer's state is always a valid solution. That is, any admissible region map from a space-based observation will intersect with any other map from the same observing satellite at the observing satellite's state. This problem is circumvented by automatically refining the state space discretization and throwing away solutions near the observing satellite's state. Numerical examples for several observation scenarios are discussed in this paper, including LEO-on-GEO and GEO-on-GEO observations. The LEO satellite is in a circular sun-synchronous orbit at 630 km altitude, much like the SBSS System. For existing IOD techniques there are known observation geometries that experience singularities such as the GEO-on-GEO case. Preliminary results show that our method does not suffer such singularities for the GEO-on-GEO observation scenario. This outcome is most likely due to the fact that we are combining 2 observations for a total of 8 observable variables, instead of the minimum 6, to obtain an initial orbit estimate. We believe this additional information removes the singularity from the problem.

Fujimoto, K.; Scheeres, D.

2011-09-01

321

Orbital Pseudotumor: Distinct Diagnostic Features and Management  

PubMed Central

Purpose: To provide an overview of the spectrum of diseases known as ‘idiopathic orbital inflammatory syndrome’ also known as orbital pseudotumor, with emphasis on specific diagnostic challenges in the evaluation and management of patients with this disorder. Methods: Review of the relevant literature and summarize recent findings regarding the epidemiology, diagnosis, pathophysiology and treatment of orbital pseudotumor. Results: Orbital pseudotumor is a benign intraorbital process confined to the orbit but extra orbital involvement can occur. It is among the 3rd most common orbital diseases along with thyroid orbitopathy and lymphoproliferative disorder and accounts for 5-10% of orbital processes. Clinically, orbital pseudotumor has been categorized as myositis, dacryoadenitis, anterior, apical and diffuse process. Patients may present with diplopia, conjunctival chemosis, proptosis or abnormal computed tomography scan (CT-scan) findings. Patients may also have associated optic neuropathy. Diagnosis is based on careful history, ultrasonography (U/S), CT-scan and magnetic resonance imaging (MRI) studies which may also provide prognostic information. Treatment consists of systemic corticosteroids in the form of oral or intravenous administration. Confirmation is made by orbital biopsy. In addition to radiation, cytotoxic agents, immunosuppressant, IV immunoglobulin, biological therapy, TNF-alpha inhibitor monoclonal antibody and Mycophenolate Moftil have been found to be useful in the management of refractory orbital pseudotumor. Conclusion: Understanding of the clinical features of patients with orbital pseudotumor, differentiating it from other orbital processes by use of imaging techniques and timely implementation of available treatment strategies may help prevent visual loss and associated morbidity from this condition.

Chaudhry, Imtiaz A; Shamsi, Farrukh A; Arat, Yonca O; Riley, Fenwick C

2008-01-01

322

MOOSE: Manned On-Orbit Servicing Equipment  

NASA Astrophysics Data System (ADS)

The ability to service satellites has thus far been limited to low earth orbit platforms within reach of the Space Shuttle. Other orbits, such as geosynchronous orbits containing high-value spacecraft have not been attainable by a servicing vehicle. The useful life of a satellite can be extended by replacing spent propellant and damaged orbital replacement units, forestalling the need for eventual replacement. This growing need for satellite on-orbits servicing can be met by the Manned On-Orbit Servicing Equipment (MOOSE). Missions requiring orbit transfer capability, precision manipulation and maneuvering, and man-in-the-loop control can be accomplished using MOOSE. MOOSE is a flexible, reusable, single operator, aerobraking spacecraft designed to refuel, repair, and service orbiting spacecraft. MOOSE will be deployed from Space Station Freedom, (SSF), where it will be stored, resupplied, and refurbished.

Budinoff, J.; Leontsinis, N.; Lane, J.; Singh, R.; Angelone, K.; Boswell, C.; Chamberlain, I.; Concha, M.; Corrodo, M.; Custodio, O.

323

Transnasal endoscopic surgery for benign orbital tumors.  

PubMed

Two cases of orbital tumor are presented, and the surgical technique by means of an endoscopic transnasal approach is discussed. In Case 1, a non-vascular, benign tumor was located inside the orbit, and it was able to be completely removed, without any complications. The tumor in Case 2 was also located inside the orbit, but it was determined to be a hemangioma based on the intraoperative pathology. To avoid eye complications arising from performance of the surgery in the presence of bleeding, it was decided to widely open the orbital lamina papyracea and periosteum, and perform only orbital decompression. The eye symptoms disappeared in both patients. Endoscopic transnasal surgery is indicated for benign orbital tumors that are medially located in the orbit. It can be thought that the eye symptoms can be alleviated by avoiding orbital pressure, regardless of whether-based on the intraoperative pathology-the tumor is completely removed or not. PMID:22595376

Haruna, Shinichi; Tukidate, Toshiharu; Konno, Wataru; Fukami, Satoshi; Nakajima, Itsuo

2012-05-15

324

Geostationary Orbital Estimation Using a Kalman Filter.  

National Technical Information Service (NTIS)

The ability of a sequential Kalman filter to predict a geostationary and an approximately geostationary orbit is assessed by comparison with the corresponding orbits predicted by a least-squares batch estimator. Prior to performing this comparison, the pe...

G. B. Sincarsin

1986-01-01

325

Autonomous Space Processor for Orbital Debris.  

National Technical Information Service (NTIS)

This work continues to develop advanced designs toward the ultimate goal of a GETAWAY SPECIAL to demonstrate economical removal of orbital debris utilizing local resources in orbit. The fundamental technical feasibility was demonstrated last year through ...

K. Ramohalli D. Campbell J. P. Brockman B. Carter L. Donelson

1989-01-01

326

Rational orbits around charged black holes  

NASA Astrophysics Data System (ADS)

We show that all eccentric timelike orbits in Reissner-Nordström spacetime can be classified using a taxonomy that draws upon an isomorphism between periodic orbits and the set of rational numbers. By virtue of the fact that the rationals are dense, the taxonomy can be used to approximate aperiodic orbits with periodic orbits. This may help reduce computational overhead for calculations in gravitational wave astronomy. Our dynamical systems approach enables us to study orbits for both charged and uncharged particles in spite of the fact that charged particle orbits around a charged black hole do not admit a simple one-dimensional effective potential description. Finally, we show that comparing periodic orbits in the Reissner-Nordström and Schwarzschild geometries enables us to distinguish charged and uncharged spacetimes by looking only at the orbital dynamics.

Misra, Vedant; Levin, Janna

2010-10-01

327

Orbits and Interiors of Planets  

NASA Astrophysics Data System (ADS)

The focus of this thesis is a collection of problems of timely interest in orbital dynamics and interior structure of planetary bodies. The first three chapters are dedicated to understanding the interior structure of close-in, gaseous extrasolar planets (hot Jupiters). In order to resolve a long-standing problem of anomalously large hot Jupiter radii, we proposed a novel magnetohydrodynamic mechanism responsible for inflation. The mechanism relies on the electro-magnetic interactions between fast atmospheric flows and the planetary magnetic field in a thermally ionized atmosphere, to induce electrical currents that flow throughout the planet. The resulting Ohmic dissipation acts to maintain the interior entropies, and by extension the radii of hot Jupiters at an enhanced level. Using self-consistent calculations of thermal evolution of hot Jupiters under Ohmic dissipation, we demonstrated a clear tendency towards inflated radii for effective temperatures that give rise to significant ionization of K and Na in the atmosphere, a trend fully consistent with the observational data. Furthermore, we found that in absence of massive cores, low-mass hot Jupiters can over-flow their Roche-lobes and evaporate on Gyr time-scales, possibly leaving behind small rocky cores. Chapters four through six focus on the improvement and implications of a model for orbital evolution of the solar system, driven by dynamical instability (termed the "Nice" model). Hydrodynamical studies of the orbital evolution of planets embedded in protoplanetary disks suggest that giant planets have a tendency to assemble into multi-resonant configurations. Following this argument, we used analytical methods as well as self-consistent numerical N-body simulations to identify fully-resonant primordial states of the outer solar system, whose dynamical evolutions give rise to orbital architectures that resemble the current solar system. We found a total of only eight such initial conditions, providing independent constraints for the solar system's birth environment. Next, we addressed a significant drawback of the original Nice model, namely its inability to create the physically unique, cold classical population of the Kuiper Belt. Specifically, we showed that a locally-formed cold belt can survive the transient instability, and its relatively calm dynamical structure can be reproduced. The last four chapters of this thesis address various aspects and consequences of dynamical relaxation of planetary orbits through dissipative effects as well as the formation of planets in binary stellar systems. Using octopole-order secular perturbation theory, we demonstrated that in multi-planet systems, tidal dissipation often drives orbits onto dynamical "fixed points," characterized by apsidal alignment and lack of periodic variations in eccentricities. We applied this formalism towards investigating the possibility that the large orbital eccentricity of the transiting Neptune-mass planet Gliese 436b is maintained in the face of tidal dissipation by a second planet in the system and computed a locus of possible orbits for the putative perturber. Following up along similar lines, we used various permutations of secular theory to show that when applied specifically to close-in low-mass planetary systems, various terms in the perturbation equations become separable, and the true masses of the planets can be solved for algebraically. In practice, this means that precise knowledge of the system's orbital state can resolve the sin( i) degeneracy inherent to non-transiting planets. Subsequently, we investigated the onset of chaotic motion in dissipative planetary systems. We worked in the context of classical secular perturbation theory, and showed that planetary systems approach chaos via the so-called period-doubling route. Furthermore, we demonstrated that chaotic strange attractors can exist in mildly damped systems, such as photo-evaporating nebulae that host multiple planets. Finally, we considered planetary formation in highly inclined binary systems,

Batygin, Konstantin

2012-05-01

328

Atmosphere and orbital stability of exosolar planets orbiting gamma Cephei  

Microsoft Academic Search

The recently discovered Jupiter-like planet (m sin i= 1.76 M_jup) in the binary system gamma Cephei moves in a so-called S-type orbit around its host-star with a distance of about 2.15 AU. It is the first planet that have been found in a close binary and is from the dynamical point of view a very stable configuration. Numerical computations in

H. Lammer; R. Dvorak; E. Pilat-Lohinger; B. Funk; F. Freistetter; I. Ribas; F. Selsis; E. F. Guinan; W. W. Weiss; S. J. Bauer

2003-01-01

329

Orbital apex leiomyoma with intracranial extension  

Microsoft Academic Search

BACKGROUNDLeiomyoma is a rare, benign smooth muscle tumor of the orbit. It occasionally shows some histologic resemblance to other common tumors of the orbit like neurofibroma and schwannoma. Its location at the orbital apex is uncommon and only one case with intracranial extension has been reported so far.CASE DESCRIPTIONA nine-year-old boy presented to us with left orbital pain. Four years

Vaijayantee Kulkarni; Vedantam Rajshekhar; Sushil M Chandi

2000-01-01

330

Orbital complications after aqueous drainage device procedures.  

PubMed

A retrospective case series of 2 patients with orbital complications after tube shunt placement for glaucoma is reported. The first patient presented with limited motility and conjunctival injection in the setting of intraocular gas leakage in the superior orbit after previous vitreoretinal surgery. The second patient presented with multiple signs of orbital cellulitis. Both patients improved with intravenous antibiotics. Although rare, orbital complications may occur after glaucoma tube shunt surgery. PMID:15677956

Marcet, Marcus M; Woog, John J; Bellows, A Robert; Mandeville, John T; Maltzman, Jeffrey S; Khan, Jemshed

2005-01-01

331

Circulant Orbitals for Atoms and Molecules  

Microsoft Academic Search

Circulant orbitals phi n for a closed-shell system are the orbitals obtained when the N canonical orthonormal Hartree-Fock orbitals lambda ell are subjected to a unitary transformation which is the discrete Fourier transformation. phi n=1\\/sqrt{N}sumelllambda ellomega (n-1)(ell -1), where omega =exp (2pi i\\/N). Electron densities associated with the orbitals phi n are each close to the average total electron density.

Robert G. Parr; Min-Bo Chen

1981-01-01

332

Frozen orbit analysis in the Martian system  

Microsoft Academic Search

A frozen orbit is an orbit whose time rate of change of the argument of the periapsis, the eccentricity, the semi major axis, or the angle of inclination (i) is approximately equal to zero. Martian frozen orbits are known to exist for polar trajectories with altitudes from 300 km to 1000 km. The objective of this study was to determine

James W. Foister III

1987-01-01

333

Determination and prediction of Magellan's orbit  

Microsoft Academic Search

The Magellan spacecraft has been systematically mapping the surface of Venus since September 15, 1990, using a synthetic aperture radar. The spacecraft orbit about Venus is nearly polar, with an orbital period of 3.26 hours and periapsis altitude of 295 km. The radiometric measurements and the data reduction method used to determine and predict the spacecraft state are described. Orbit

D. B. Engelhardt; J. B. McNamee; S. K. Wong; F. G. Bonneau; E. J. Graat; R. J. Haw; G. R. Kronschnabl; M. S. Ryne

1991-01-01

334

Orbit Deformities in Craniofacial Neurofibromatosis Type 1  

Microsoft Academic Search

BACKGROUND AND PURPOSE: The possible relationship of orbit deformities in neurofi- bromatosis type 1 (NF1) to plexiform neurofibromas (PNFs) have not been fully elucidated. Our purpose was to review orbital changes in patients with craniofacial NF1. METHODS: We retrospectively reviewed CT and MR imaging abnormalities of the orbit in 31 patients (18 male, 13 female; mean age, 14 years; age

Claude Jacquemin; Thomas M. Bosley; Helena Svedberg

335

Some Observations on Molecular Orbital Theory  

ERIC Educational Resources Information Center

|A few flawed predictions in the context of homonuclear diatomic molecules are presented in order to introduce students to molecular orbital (MO) theory. A common misrepresentation of the relationship between the energy of an atomic orbital and the energy of the MO associated with the atomic orbital is illustrated.|

Journal of Chemical Education, 2005

2005-01-01

336

Orbit lifetime characteristics for Space Station  

Microsoft Academic Search

The factors that influence the orbital lifetime characteristics of the NASA Space Station are discussed. These include altitude, attitude, launch date, ballistic coefficient, and the presence of large articulating solar arrays. Examples from previous program systems studies are presented that illustrate how each factor affects Station orbit lifetime. The effect of atmospheric density models on orbit lifetime predictions is addressed

L. Deryder; G. M. Kelly; M. Heck

1988-01-01

337

What's New for Laser Orbital Debris Removal  

Microsoft Academic Search

Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the use of space is threatened by runaway collision cascading. A problem predicted more than thirty years ago, the threat from debris larger than about 1cm is now a reality that we ignore at our peril. The least costly, and most comprehensive, solution is Laser Orbital Debris Removal

Claude Phipps; Mike Lander

2011-01-01

338

The Meaning of d-Orbital Labels  

ERIC Educational Resources Information Center

|The orbital labels when considered as the angular part of the wavefunction can serve as an inclusive principle, which the students can use to construct the spatial shapes of the d orbitals from their labels. The spatial orientation of the different d orbitals guides the crystal field theory which includes d(sub xy), d(sub yz) and d(sub xz) lying…

Ashkenazi, Guy

2005-01-01

339

NASA's Lunar Reconnaissance Orbiter Cameras (LROC)  

Microsoft Academic Search

The Lunar Reconnaissance Orbiter LRO mission is scheduled to launch in the fall of 2008 as part of NASA s Robotic Lunar Exploration Program and is the first spacecraft to be built as part of NASA s Vision for Space Exploration The orbiter will be equipped with seven scientific instrument packages one of which is LROC The Lunar Reconnaissance Orbiter

M. Robinson; A. McEwen; E. Eliason; B. Joliff; H. Hiesinger; M. Malin; P. Thomas; E. Turtle; S. Brylow

2006-01-01

340

Distant quasi-periodic orbits around Mercury  

NASA Astrophysics Data System (ADS)

In this paper, distant quasi-periodic orbits around Mercury are studied for future Mercury missions. All of these orbits have relatively large sizes, with their altitudes near or above the Mercury sphere of influence. The research is carried out in the framework of the elliptic restricted three-body problem (ER3BP) to account for the planet's non-negligible orbital eccentricity. Retrograde and prograde quasi-periodic trajectories in the planar ER3BP are generalized from periodic orbits in the CR3BP by the homotopy algorithm, and the shape evolution of such quasi-periodic trajectories around Mercury is investigated. Numerical simulations are performed to evaluate the stability of these distant orbits in the long term. These two classes of orbits present different characteristics: retrograde orbits can maintain shape stability with a large size, although the trajectories in some regions may oscillate with larger amplitudes; for prograde orbits, the range of existence is much smaller, and their trajectories easily move away from the vicinity of Mercury when the orbits become larger. Distant orbits can be used to explore the space environment in the vicinity of Mercury, and some orbits can be taken as transfer orbits for low-cost Mercury return missions or other programs for their high maneuverability.

Ma, Xue; Li, Junfeng

2013-01-01

341

Stability Analysis of the Europa Orbiter  

Microsoft Academic Search

A study of the Europa orbiter is made using numerical and analytical techniques. This study is motivated by the fact that numerically integrated, low altitude spacecraft orbits about Europa will often impact on that moon's surface after a short period of a few days to weeks. Numerical integrations indicate that these impact orbits only occur for inclinations within ? 45?

D. J. Scheeres; M. D. Guman

342

Idiopathic Orbital Inflammation Syndrome with Retro-Orbital Involvement: A Retrospective Study of Eight Patients  

PubMed Central

Background The aim of this retrospective study was to document the clinical findings and radiological features of idiopathic orbital inflammation syndrome with retro-orbital involvement. Methods We searched for ophthalmological patients who received orbital imaging at Zhejiang Provincial People's Hospital between October 2003 and April 2010. Seventy-three patients were diagnosed with idiopathic orbital inflammation syndrome based on clinicoradiological features, with pathological confirmation of nonspecific inflammatory conditions in 47 patients. Eight patients (11%) had MRI or CT evidence of retro-orbital involvement. All 8 patients were diagnosed with idiopathic orbital inflammation syndrome after biopsy of the orbital lesion. MR images were obtained for all 8 patients; 3 patients also had a contrast-enhanced CT scan. Results Seven out of 8 patients with retro-orbital involvement also had orbital apex lesions. Of the 65 patients without retro-orbital involvement, 19 had orbital apex lesions. The difference in the number of patients with orbital apex lesions between the two populations was significant (Fisher exact test P?=?.002). In all 8 patients with retro-orbital involvement, the inflammation spread through the superior orbital fissure. The retro-orbital lesions were isointense to grey matter on T1-weighted images, hypointense on T2-weighted images, and displayed uniform contrast enhancement; on contrast-enhanced CT scans, they were hyperdense relative to the contralateral mirror area and had radiological contours that were similar to those seen on MR images. The diffuse inflammation with marked sclerosis and hyalinization that we observed in the patients with retro-orbital involvement is consistent with the diagnosis of the sclerosing subtype of idiopathic orbital inflammation syndrome. All 8 patients also complained of mild to moderate periorbital pain (headache). Conclusions In patients with idiopathic orbital inflammation syndrome, it is important to perform MRI and CT scans to identify possible retro-orbital involvement. Retro-orbital involvement is more frequent when the lesion is present in the orbital apex.

Li, Yumei; Lip, Gerald; Chong, Vincent; Yuan, Jianhua; Ding, Zhongxiang

2013-01-01

343

Inflammatory pseudotumor of the orbit.  

PubMed

The history and confusing terminology regarding reports of inflammatory pseudotumor of the orbit are reviewed. The wide clinical spectrum and variety of associated conditions is emphasized. Twenty-seven patients from the Wills Eye Hospital with clinical records and histopathologic material consistent with orbital pseudotumor were reviewed and an attempt was made to correlate the histopathologic findings with clinical presentation, response to steroids, and final outcome. Adequate follow-up averaging 3.6 years was obtained in 17 cases. Most cases in the series had a favorable outcome, and patients demonstrating the acute and subacute stages of Type II patterns responded to systemic steroids. Repeated and extensive surgical intervention appear to be harmful. PMID:576377

Heersink, B; Rodrigues, M R; Flanagan, J C

1977-01-01

344

Orbital migration models under test  

NASA Astrophysics Data System (ADS)

Planet-disk interaction predicts a change in the orbital elements of an embedded planet. Through linear and fully hydrodynamical studies it has been found that migration is typically directed inwards. Hence, this migration process gives natural explanation for the presence of the 'hot' planets orbiting close to the parent star, and it plays a mayor role in explaining the formation of resonant planetary systems. However, standard migration models for locally isothermal disks indicate a too rapid inward migration for small mass planets, and a large number of massive planets are found very far away from the star. Recent studies, including more complete disk physics, have opened up new paths to slow down or even reverse migration. The new findings on migration are discussed and connected to the observational properties of planetary systems.

Kley, Wilhelm

2011-11-01

345

SILEX in-orbit performances  

NASA Astrophysics Data System (ADS)

PASTEL embarked on-board SPOT4, French LEO earth observation satellite, and OPALE mounted on-board ARTEMIS, European GEO telecommunication satellite are the key components of SILEX (Semi-conductor Inter-satellite Link Experiment) system. Launched in March 1998, PASTEL terminal was first verified via star tracking. Then, first SILEX optical communication was successfully performed in December 2001 with ARTEMIS at 31000 km. Following 12 months ARTEMIS orbit rising, SILEX commissioning phase was successfully achieved in spring 2003. Today, more than hundred successful optical communications have been achieved. On 1st of October 2003, the SILEX optical link was declared fully operational by the European and French space agencies. After a recall of SILEX architecture, design and on-ground verification, this paper reports on in-orbit results.

Planche, Gilles; Chorvalli, Vincent

2004-06-01

346

Of Orbits, Conics, and Grammar  

NASA Astrophysics Data System (ADS)

In the half-dozen or so years leading up to the publication of the Principia, Isaac Newton observed the comets of 1680 and 1682 and wrestled with the extent to which his law of gravitation could be applied. In time, he would see the connections between the four possible orbits of a satellite (circular, elliptical, parabolic, and hyperbolic) and the four curves produced by the careful carving of a cone. But if we look a little further into the conic sections, we find some interesting connections among the natural orbit of a satellite, ancient mathematics, and the roots of familiar words. Illuminating these connections for introductory physics students may help them to better understand the role of language and mathematics in the descriptions of science.

Henderson, Hugh

2005-02-01

347

An orbit averaged particle code  

Microsoft Academic Search

A new method for efficient computer simulation of long time-scale plasma physics phenomena is proposed which has proved successful in one- and two-dimensional magneto-inductive particle codes. The method relies on orbit-averaging charge and current densities in Maxwell's equations before solving for the self-consistent electric and magnetic fields in order to filter out unwanted high-frequency oscillations and reduce the number of

B. I. Cohen; T. A. Brengle; D. B. Conley; R. P. Freis

1980-01-01

348

Thrust aided sub-orbits  

Microsoft Academic Search

A discussion on thrust assisted sub-orbits is presented. This operation may be considered as a candidate means for providing station-keeping, for the interrogation of circulating satellites, and as an operational maneuver for pick-up, launch and\\/or inspection of experiment modules (and the like) from (say) the SHUTTLE spacecraft. Examples, drawn from theoretical developments, are presented. These describe both the requirements and

J. B. Eades Jr.

1977-01-01

349

Ganymede's Thermal and Orbital Evolution  

NASA Astrophysics Data System (ADS)

The heating mechanism that created the melting and global expansion necessary to form Ganymede's ubiquitous grooved terrains remains unclear. While the current Laplace resonance does not pump Ganymede's eccentricity, Malhotra (1991) and Showman and Malhotra (1997) showed that the Galilean satellites may have passed through Laplace-like resonances that did force Ganymede's eccentricity, leading to internal heating of the satellite. Showman et al. (1997) explored the effects of such tidal heating on Ganymede and found that it can lead to thermal runaway and melting, helping to explain the extensive resurfacing of the satellite. While the likelihood of thermal runaway appeared small, improved understanding of the internal structure of Ganymede and the nature of stagnant lid convection warrants a new study. Here we present simulations of Ganymede's coupled thermal and orbital evolution. The orbital model allows a dynamical investigation of the orbital histories of the Galilean satellites near the observed 2:1 mean motion resonance. The thermal model simultaneously solves the energy balance in Ganymede's ice shell, silicate mantle, and Fe/FeS core. Stagnant lid convection, radiogenic heating, ocean formation, and inner core growth are included in the model. Coupling between the orbital and thermal models occurs via tidal dissipation, which uses the model of Tobie et al. 2005 to determine how tidal heating is distributed throughout the satellite interior. These simulations reveal that passage through the Laplace-like resonance can lead to melting under a much broader range of initial conditions than suggested by Showman et al. (1997). Such melting requires that the grain sizes in Ganymede's icy mantle be 1 mm or less, and that the Galilean satellites passed through one of the stronger Laplace-like resonances. The generation of melt would not only lead to satellite expansion and extensional stress, but would also provide a source of near surface melt, permitting cryovolcanic activity.

Bland, Michael T.; Showman, A. P.; Tobie, G.

2007-10-01

350

Techniques of orbital regional anaesthesia  

Microsoft Academic Search

1.0-1.5 cm from the apex of the orbit. Local anaesthetics, in blocking concentrations, have to reach an exposed 5-10-mm segment of these motor nerves in the posterior intracone space for con- duction block of those nerves and akinesia of their supplied muscles to occur. Retained activity of the superior oblique muscle is frequently seen after intraconal local anaesthetic injection because

R. C. HAMILTON

351

Introduction to complex orbital momenta  

Microsoft Academic Search

Summary  In this paper the orbital momentumj, until now considered as an integer discrete parameter in the radial Schrödinger wave equations, is allowed to take complex\\u000a values. The purpose of such an enlargement is not purely academic but opens new possibilities in discussing the connection\\u000a between potentials and scattering amplitudes. In particular it is shown that under reasonable assumptions, fulfilled by

T. Regge

1959-01-01

352

Ionospheric Imaging from Geostationary Orbit  

Microsoft Academic Search

An ultraviolet imager is under development to image the ionosphere and thermosphere from geostationary orbit. The instrument will consist of two telescopes, one with a filter wheel to measure the atomic oxygen airglow emission at 130.4 nm and 135.6 nm and molecular nitrogen Lyman-Birge-Hopfield bands near 142.5 nm. The second telescope will image the atomic oxygen ion resonance multiplet at

R. P. McCoy; K. S. Wood; K. F. Dymond; S. E. Thonnard

2001-01-01

353

Mutual Orbits of Transneptunian Binaries  

NASA Astrophysics Data System (ADS)

We report the latest results from a program of high spatial resolution imaging to resolve the individual components of binary transneptunian objects. These observations use Hubble Space Telescope and also laser guide star adaptive optics systems on Keck and Gemini telescopes on Mauna Kea. From relative astrometry over multiple epochs, we determine the mutual orbits of the components, and thus the total masses of the systems. Accurate masses anchor subsequent detailed investigations into the physical characteristics of these systems. For instance, dynamical masses enable computation of bulk densities for systems where the component sizes can be estimated from other measurements. Additionally, patterns in the ensemble characteristics of binary orbits offer clues to circumstances in the protoplanetary nebula when these systems formed, as well as carrying imprints of various subsequent dynamical evolution processes. The growing ensemble of known orbits shows intriguing patterns that can shed light on the evolution of this population of distant objects. This work has been supported by an NSF Planetary Astronomy grant and by several Hubble Space Telescope and NASA Keck data analysis grants. The research makes use of data from the Gemini Observatory obtained through NOAO survey program 11A-0017, from a large number of Hubble Space Telescope programs, and from several NASA Keck programs.

Grundy, William M.; Noll, K. S.; Roe, H. G.; Porter, S. B.; Trujillo, C. A.; Benecchi, S. D.; Buie, M. W.

2012-10-01

354

Management of preseptal and orbital cellulitis  

PubMed Central

Orbital cellulitis describes an infection involving the soft tissues posterior to the orbital septum, including the fat and muscle within the bony orbit. This condition may be associated with severe sight and life-threatening complications. Despite significant advances in antimicrobial therapies and diagnostic technologies, the management of orbital cellulitis often remains challenging, and rapid diagnosis and prompt initiation of therapy are important in minimizing complications and optimizing outcomes. This review summarizes the distinctive characteristics of preseptal and orbital cellulitis, with a focus on anatomic considerations, predisposing conditions, approaches to evaluation, and management strategies.

Lee, Seongmu; Yen, Michael T.

2010-01-01

355

Linear magnetoelectric effect by orbital magnetism.  

PubMed

We use symmetry analysis and first-principles calculations to show that the linear magnetoelectric effect can originate from the response of orbital magnetic moments to the polar distortions induced by an applied electric field. Using LiFePO(4) as a model compound we show that spin-orbit coupling partially lifts the quenching of the 3d orbitals and causes small orbital magnetic moments (?((L)) ? 0.3 ?(B)) parallel to the spins of the Fe(2+) ions. An applied electric field E modifies the size of these orbital magnetic moments inducing a net magnetization linear in E. PMID:23215421

Scaramucci, A; Bousquet, E; Fechner, M; Mostovoy, M; Spaldin, N A

2012-11-08

356

In-situ detection of interstellar dust at Earth orbit distance: possible delivery of pre-biotic material.  

NASA Astrophysics Data System (ADS)

Theories for an extra-terrestrial origin of life require exogenous delivery of pre-biotic compounds onto the Earth. Many studies prove that the interstellar medium contains a great diversity of such organics, mainly incorporated in cosmic dust. An indirect source of interstellar matter onto the Earth is provided by impacts of comets or asteroids, in which pre-solar dust grains are embedded. However, we show that a direct injection of interstellar dust onto the Earth also exists. A stream of interstellar sub-micrometer dust grains penetrating the solar system was identified outside 3 AU heliocentric distance by the dust instrument of the Ulysses} spacecraft. Data from the Cassini} mission and a new analysis of the Helios} and Galileo} dust instruments data show the deep penetration of the interstellar dust stream down to the terrestrial planets orbits. Despite of heliospheric filtering through radiation pressure and electromagnetic interactions, an interstellar dust flux of about 3.10-5m-2s-1 reaches the Earth. The typical radius of in-situ detected grains falling on Earth is about 0.4 ?m. Furthermore, the Helios} data suggest that bigger grains can also be accreted with seasonal variations, through gravitational focusing. In addition, a rough insight into the elemental composition of big interstellar grains can be inferred from the time-of-flight mass spectra obtained by the Helios} dust instrument.

Altobelli, N.; Gruen, E.; Kempf, S.; Krueger, H.; Landgraf, M.; Srama, R.

357

Prospective Ukrainian lunar orbiter mission  

NASA Astrophysics Data System (ADS)

Ukraine has launch vehicles that are able to deliver about 300 kg to the lunar orbit. Future Ukrainian lunar program may propose a polar orbiter. This orbiter should fill principal information gaps in our knowledge about the Moon after Clementine and Lunar Prospector missions and the future missions, like Smart-1, Lunar-A, and Selene. We consider that this can be provided by radar studies of the Moon with supporting optical polarimetric observations from lunar polar orbit. These experiments allow one to better understand global structure of the lunar surface in a wide range of scales, from microns to kilometers. We propose three instruments for the prospective lunar orbiter. They are: a synthetic aperture imaging radar (SAR), ground-penetrating radar (GPR), and imaging polarimeter (IP). The main purpose of SAR is to study with high resolution (50 m) the permanently shadowed sites in the lunar polar regions. These sites are cold traps for volatiles, and have a potential of resource utilization. Possible presence of water ice in the regolith in the sites makes them interesting for permanent manned bases on the Moon. Radar imaging and mapping of other interesting regions could be also planned. Multi-frequencies multi-polarization soun d ing of the lunar surface with GPR can provide information about internal structure of the lunar surface from meters to several hundred meters deep. GPR can be used for measuring the megaregolith layer properties, detection of cryptomaria, and studies of internal structure of the largest craters. IP will be a CCD camera with an additional suite of polarizers. Modest spatial resolution (100 m) should provide a total coverage or a large portion of the lunar surface in oblique viewing basically at large phase angles. Polarization degree at large (>90°) phase angles bears information about characteristic size of the regolith particles. Additional radiophysical experiments are considered with the use of the SAR system, e.g., bistatic radar sounding with the onboard transmitter and Earth-based receiver and i terferometry with the onboardn transmitter and two Earth-based receiving antennas that allows reconstruction of surface topography with high resolution.

Shkuratov, Y.; Litvinenko, L.; Shulga, V.; Yatskiv, Y.; Kislyuk, V.

358

A Southern Hemisphere radar meteor orbit survey  

NASA Astrophysics Data System (ADS)

A meteor radar system has been operated on a routine basis near Christchurch, New Zealand, to determine the orbits of Earth-impacting interplanetary dust and meteoroids. The system sensitivity is +13 visual magnitude, corresponding to approximately 100 micron sized meteoroids. With an orbital precision of 2 degrees in angular elements and 10 percent in orbital energy (1/a), the operation yields an average of 1500 orbits daily with a total to date in excess of 105. The use of pc's and automated data reduction permit the large orbital data sets we collect to be routinely reduced. Some illustrative examples are presented of the signal formats/processing and the results of data reduction, giving the individual orbital elements and hence the overall distributions. Current studies include the distribution of dust in the inner solar system; the influx of meteoroids associated with near-Earth asteroids; and the orbital structure existing in comet-produced streams.

Baggaley, W. Jack; Steel, Duncan I.; Taylor, Andrew D.

359

A review of aeroassisted orbit transfer  

NASA Astrophysics Data System (ADS)

The development of a theory of aeroassisted orbital plane change maneuvers and necessary equipment is traced and an assessment is made of potential applications. Synergetic plane changes are effected through a combination of aerodynamic and propulsive forces involving the dip of an orbiting vehicle into the atmosphere, performance of an aerodynamic turn using thrust if necessary, then reboosting into a reconfigured orbit. The Orbiter is noted to possess large synergetic plane change capability, and configurations of spacecraft such as the Venus Orbiting Imaging radar for using aeroassist to brake interplanetary velocities before establishing orbits are described. Technology advances necessary to construct effective aerobrake, aerocapture, and orbital transfer vehicles are explored, including fabrication of inflatable ballutes, lighter L/D configurations, and lifting brakes, which are considered to be minor extensions of current capabilities.

Walberg, G. D.

1982-08-01

360

Orbital Magnetization in Periodic Insulators  

NASA Astrophysics Data System (ADS)

Recent years have seen a surge of interest in issues of charge and spin transport in magnetic materials and nanostructures, including anomalous Hall and spin Hall effects. In this context, it is quite surprising that the theory of orbital magnetization has remained in a condition similar to that of the polarization before the early 1990s, when the problem of computing finite polarization changes was solved by the introduction of the Berry-phase theory. The essential difficulty, that the matrix elements of the position operator r are not well-defined in the Bloch representation, could be overcome by reformulating the problem in the Wannier representation. In order to derive an analogue theory for the orbital magnetization, we again work in the Wannier representation and assume a periodic insulator with broken time-reversal symmetry, vanishing (or commensurate) magnetic field, and zero Chern numbers. We show that by replacing the dipole operator r with the circulation operator rxv, only one contribution to the magnetization is found, i.e., the magnetization associated with the internal circulation of bulk-like Wannier functions. The missing contribution arises from net currents carried by the Wannier functions at the boundary of the sample. We prove that both contributions can be expressed as bulk properties in terms of Bloch functions in a gauge-invariant way.ootnotetextT. Thonhauser, Davide Ceresoli, David Vanderbilt, and R. Resta, Phys. Rev. Lett. 95, 137,05 (2005). Our expression for the orbital magnetization is verified by comparing numerical tight-binding calculations for finite and periodic samples. Possible extensions to metals or insulators with non-zero Chern numbers will also be discussed. R. King-Smith and D. Vanderbilt, Phys. Rev. B 47, 1651 (1993).

Thonhauser, Timo

2006-03-01

361

Orbital perturbations of low orbiters in a dusty Martian atmosphere  

NASA Astrophysics Data System (ADS)

A study of a low-orbit polar satellite around Mars is carried out using Lagrangian mechanics principles and Lagrange's planetary equations in which both conservative and non-conservative forces are modelled. Our work differs from state-of-the-art Newtonian and Gaussian methods and enhances the modelling of the perturbing potentials arising from areopotential anomalies: atmospheric drag, dust drag, solar radiation pressure, relativistic effects, third-body, and solid-body tides on Mars. Because we are interested in analytical/numerical expressions and results, the Lagrangian method constitutes a more suitable analytical approach than does the traditional Gaussian. The resulting system of equations of motion for the satellite provides the time derivatives of the orbital elements as functions of the gravitational harmonic coefficients and all the perturbing effects we considered. When the time derivatives of the orbital elements are available from satellite tracking observations, the equations can be used in a least-squares estimation process to provide, the gravitational field in terms of harmonic coefficients. To understand the utility of the derived equations of motion, we obtain analytical expressions for the gravitational harmonics of degree and order six. These expressions involve, among other variables, the inclination and eccentricity functions and their time derivatives. In particular, the numerical calculation of high-degree/order eccentricity and inclination functions are known to be numerically unstable. To remove such instabilities, we use an effective and efficient transformation that relates the eccentricity functions to Hansen coefficients, using Bessel functions of the first kind. Similarly, the inclination functions are transformed into hypergeometric series. Analytical and numerical tests show that the transformed inclination and eccentricity functions are remarkably stable up to degree/order eighty. This is very important when the Lagrangian method is used to determine the gravitational field with high accuracy and spatial resolution. We study the effects of atmospheric dust on low orbiters by considering a low velocity "fluid" dust medium containing dust particles of radius 1.25 mum, by deriving a velocity-cube dissipation function that represents the energy density dissipated by the satellite per unit time. We have developed a method for determining a satellite's dust drag coefficient provided that its geometrical shape is known. For example, for a cylindrical satellite, we find that Cd = 4. We also calculate an upper bound to the atmospheric dust density of 8.323 x 10-10 kg m-3 at an altitude of 100 km. Local dust storm-clouds in the range of 800 - 1000 km reduce the semi-major axis from a few centimetres up to a few decimetres per day. Similarly, episodic dust clouds of 10 km in length and at low altitudes (65 - 90 km) result in sub-millimetre per day losses in the semi-major axis. The satellite's mass increase due to dust adhesion is modelled by considering the dust as an aerosol moving in an atmospheric fluid. Adhesion affects the semi-major axis by a few millimetres to a few decimetres per year. Other orbital elements are affected only by insignificant amounts.

Haranas, Ioannis Iraklis

2010-12-01

362

[Clinical and neuroradiological diagnostics of orbital tumors].  

PubMed

Exophthalmus is the leading sign of space-occupying lesions of the orbit. Patients may further present with lid swelling, impaired ocular motility and optic neuropathy including a relative afferent pupillary defect, compressive optic disc edema or optic atrophy. Orbital tumors can be classified into various categories depending on the etiology, as lymphoproliferative lesions (in particular non-Hodgkin's lymphoma as the most common malignant orbital tumor of adulthood), optic nerve and meningeal lesions, lacrimal gland lesions, secondary orbital tumors which extend to the orbit from neighboring structures and metastases. Slightly less common are vasculogenic and cystic lesions including cavernous hemangioma as the most common benign orbital tumor of adulthood and dermoid cysts as the most common benign orbital tumor of childhood. Rhabdomyosarcoma is the most common malignant orbital tumor of childhood but has a low total incidence. Orbital tumors might not only cause symptoms like pain, diplopia and loss of visual acuity but may also lead to esthetically disfiguring changes. Particular attention should be paid to underlying systemic diseases and generalized tumor diseases. This article illustrates the approach to a detailed clinical and neuroradiological assessment which is mandatory for the care of orbital tumor patients. PMID:21695605

Poloschek, C M; Lagrèze, W A; Ridder, G J; Hader, C

2011-06-01

363

Low-thrust control of orbital elements  

NASA Astrophysics Data System (ADS)

This dissertation presents a method for controlling the orbital elements of a spacecraft using continuous low-thrust systems. The method involves the use of a general performance index, which is designed to minimize the difference between the instantaneous orbital elements of a spacecraft and some desired set of orbital elements. Due to the generality of the controller design, the resultant controller can be applied to a wide variety of scenarios about various bodies in space. To minimize the designed performance index, a shooting method and a Sequential Quadratic Programming algorithm are utilized and compared. The primary application of the general controller design in this study is the problem of generating and maintaining low-altitude, polar, Sun-synchronous orbits about the Moon. Such orbits are useful for lunar mapping missions, such as with NASA's Lunar Reconnaissance Orbiter (LRO) mission which began in June of 2009. While Sun-synchronous orbits are known to exist naturally about Earth, lunar Sun-synchronous orbits do not exist naturally and instead require a set of continuous low-thrust control actions for stationkeeping. In this dissertation, it is shown that Sun-synchronous orbits can be maintained for extended periods of time using low out-of-plane thrust levels. The steering profiles necessary for stationkeeping these orbits are shown to follow simple periodic profiles. From a literature search, this is the first known work which has studied the techniques required for maintaining Sun-synchronous orbits about the Moon. In order to demonstrate the effectiveness of the general controller design, it is also applied to two additional astronautical problems of interest. In particular, the controller design is applied to the problem of an orbit transfer between two inclined geosynchronous orbits about Earth and the problem of low-thrust asteroid deflection.

Harl, Nathan Robert

364

Orbits of 15 visual binaries  

NASA Astrophysics Data System (ADS)

Observations over the May 1981-May 1983 period are the bases of the orbital and physical data presented on 15 visual pairs which include the Hyades triple ADS 3483, the probable quadruple Zeta Sge, the red dwarf pair Kpr 99, and the stars 46 Tau, 73 Oph, and 81 Cnc. New mass ratio and parallax results are also given for six of the objects studied. Objects and elements, an ephemerides, and comparisons with observations that have for the most part been condensed into normal places, are presented in tabular form.

Heintz, W. D.

1984-04-01

365

PHOTOMETRIC ORBITS OF EXTRASOLAR PLANETS  

SciTech Connect

We define and analyze the photometric orbit (PhO) of an extrasolar planet observed in reflected light. In our definition, the PhO is a Keplerian entity with six parameters: semimajor axis, eccentricity, mean anomaly at some particular time, argument of periastron, inclination angle, and effective radius, which is the square root of the geometric albedo times the planetary radius. Preliminarily, we assume a Lambertian phase function. We study in detail the case of short-period giant planets (SPGPs) and observational parameters relevant to the Kepler mission: 20 ppm photometry with normal errors, 6.5 hr cadence, and three-year duration. We define a relevant 'planetary population of interest' in terms of probability distributions of the PhO parameters. We perform Monte Carlo experiments to estimate the ability to detect planets and to recover PhO parameters from light curves. We calibrate the completeness of a periodogram search technique, and find structure caused by degeneracy. We recover full orbital solutions from synthetic Kepler data sets and estimate the median errors in recovered PhO parameters. We treat in depth a case of a Jupiter body-double. For the stated assumptions, we find that Kepler should obtain orbital solutions for many of the 100-760 SPGP that Jenkins and Doyle estimate Kepler will discover. Because most or all of these discoveries will be followed up by ground-based radial velocity observations, the estimates of inclination angle from the PhO may enable the calculation of true companion masses: Kepler photometry may break the 'msin i' degeneracy. PhO observations may be difficult. There is uncertainty about how low the albedos of SPGPs actually are, about their phase functions, and about a possible noise floor due to systematic errors from instrumental and stellar sources. Nevertheless, simple detection of SPGPs in reflected light should be robust in the regime of Kepler photometry, and estimates of all six orbital parameters may be feasible in at least a subset of cases.

Brown, Robert A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)], E-mail: rbrown@stsci.edu

2009-09-10

366

Bayesian inference for orbital eccentricities  

NASA Astrophysics Data System (ADS)

Highest posterior density intervals (HPDIs) are derived for the true eccentricities ? of spectroscopic binaries with measured values e ? 0. These yield upper limits when e is below the detection threshold eth and seamlessly transform to upper and lower bounds when e > eth. In the main text, HPDIs are computed with an informative eccentricity prior representing orbital decay due to tidal dissipation. In an appendix, the corresponding HPDIs are computed with a uniform prior and are the basis for a revised version of the Lucy-Sweeney test, with the previous outcome ? = 0 now replaced by an upper limit ?U. Sampling experiments with known prior confirm the validity of the HPDIs.

Lucy, L. B.

2013-03-01

367

Particle physicists take to orbit  

SciTech Connect

A few particle physicists, previously researching ever more elusive particles with more and more powerful accelerators, have taken their discipline in the direction of astrophysics. From physicist built-experiments looking for signals from the cosmos, including dark matter particles, ultrahigh-energy cosmic rays, and neutrinos from the sun and distant supernoves, their state of the art detector technology is being applied to orbiting platforms. Physicists from the Stanford linear accelerator Laboratory are working on plans for a gamma ray telescope, and at CERN, a group of physicists are searching for signs of primordial antimatter in the universe.

Taubes, G.

1996-01-12

368

Mars Climate Orbiter Mishap Report  

NSDL National Science Digital Library

This Review Panel Report represents the work of a review team contracted by NASA to analyze its programs and practices. Released this week, the report discusses findings relating to the failure of the Mars Climate Orbiter on September 23, 1999. The report also summarizes lessons learned from the mishap, gives an overview of NASA project management, identifies common themes related to recent failures, and makes recommendations for improving the likelihood of future success for NASA missions. An additional report, from the Mars Independent Assessment Team chaired by Thomas Young, will be available by the end of March.

369

Bulk properties of the fast and slow solar wind and ICMEs measured at Ulysses: Three polar orbits of data  

NASA Astrophysics Data System (ADS)

The Ulysses spacecraft is currently in its third polar orbit of the Sun. Instruments onboard this spacecraft have made observations of the interplanetary plasma and magnetic field for over fifteen years, a timeframe which coincides with the declining phase of solar cycle 22 and all of solar cycle 23. This study combines measurements from Ulysses' plasma instrument (SWOOPS) and magnetometers (VHM/FGM) for all three orbits in order to analyze the properties of three distinct types of interplanetary plasma: the slow (< 500km/s) and fast (> 650 km/s) solar wind and interplanetary coronal mass ejections (ICMEs). The intervals of ICME plasma were obtained from the existing Ulysses-SWOOPS ICME list to which we have added 27 events identified in the 2003 through October, 2007 data. We then investigate the radial and latitudinal variation of several plasma and magnetic field parameters (vp , Tp , np , He++ /H, B, ?) from ° ° 1.3 to 5.4 AU and 80.2 N to 80.2 S, respectively. In comparison to the normal solar wind, the properties of the slow solar wind are more variable at all distances and have a slightly different radial dependence, most notably in the proton temperature. The evolution of the ICME parameters with heliocentric distance was not significantly different to that observed for the solar wind. Finally, after accounting for the radial variations, we found both the slow and fast solar wind to be relatively constant with heliolatitude, with the slow wind cooler and more dense. We have yet to identify any significant latitudinal gradients in the ICME parameters.

Ebert, Robert W.; McComas, David; Elliott, H. A.; Forsyth, R. J.; Gosling, J. T.

370

I: PRECISE ORBIT DETERMINATION AND GRAVITY FIELD MODELLING: Strategies for Precise Orbit Determination of Low Earth Orbiters Using the GPS  

NASA Astrophysics Data System (ADS)

Considerable experience accumulated during the past decade in strategies for processing GPS data from ground-based geodetic receivers. First experience on the use of GPS observations from spaceborne receivers for orbit determination of satellites on low altitude orbits was gained with the launch of TOPEX/POSEIDON ten years ago. The launch of the CHAMP satellite in July 2000 stimulated a number of activities worldwide on improving the strategies and algorithms for orbit determination for Low Earth Orbiters (LEOs) using the GPS. Similar strategies as for ground-based receivers are applied to data from spaceborne GPS receivers to determine high precision orbits. Zero- and double-differencing techniques are applied to obtain kinematic and/or reduced-dynamic orbits with an accuracy which is today at the decimeter level. Further developments in modeling and processing strategies will continuously improve the quality of GPS-derived LEO orbits in the near future. A significant improvement can be expected from fixing double-difference phase ambiguities to integer numbers. Particular studies focus on the impact of a combined processing of LEO and GPS orbits on the quality of orbits and the reference frame realization.

Hugentobler, U.; Beutler, G.

2003-07-01

371

GPS-LEO orbiter occultation orbital analyses and event determination  

NASA Astrophysics Data System (ADS)

A good knowledge of the vertical profiles of temperature and humidity throughout the atmosphere are crucial to understand the present state of the Earth's atmosphere and it's modeling. The application of radio occultation technique has a heritage of over 2 decades in NASA's planetary exploration program to study the atmosphere of most of the major bodies in the solar system. Results from NASA's planetary program experiment have proven to be very effective at characterizing the atmosphere of a planet. However, the use of radio occultation technique to remote sensing the Earth's atmosphere is only practical to be implemented recently with the advent of the matured Global Positioning System (GPS). The GPS occultation technique is well suited to observe the Earth's atmosphere, due to it excellent geographical coverage, all weather capability, long-term stability, self-calibration and high vertical resolution. The GPS/MET (GPS Meteorology) experiment launched in April 1995 is the proof-of-concept of this technique. The results from this experiment is appealing and shown that the GPS occultation technique is a promising candidate to monitor the Earth's atmosphere. With the advancement of receiver technologies and lower system cost, the GPS occultation technique is a promising tool to predict the long-term climatic changes and numerical weather modeling of the Earth's atmosphere at a higher precision. This paper briefly describes the radio occultation concept and the GPS satellite systems, which form the basis understanding of this subject matter. This is followed by a detail description of the occultation geometries between the GPS satellites and a LEO orbiter. A method to determine the occultation event is discussed and thoroughly analyzed in terms of orbit inclinations, altitudes, receiver sampling rates, antenna positioning (aft and fore pointing), and antenna mask angles. A simulator is developed using MATLAB for the orbital analyses and occultation determination in 2-D and 3-D display and in GISO (Gall Isographic) map to give the overall picture on the total occultation events per day. Finally, results are presented and discussed.

Abdul Rashid, Z. A.; Cheng, P. P.

2003-04-01

372

Orbital inflammation after dental procedures.  

PubMed

This study reports 3 cases of acute orbital inflammation that occurred within 3 weeks of various dental procedures and offers a possible mechanism as to their cause. The charts of 3 patients were retrospectively examined. Clinical notes, laboratory testing, and imaging studies were reviewed. The cases involved a 36-year old woman, a 61-year-old woman, and a 44-year-old woman who developed acute dacryoadenitis after tooth extraction in the former case and after routine dental cleaning in the latter 2. All cases were initially treated with an oral steroid taper over 6 to 8 weeks. The first 2 cases resolved promptly and have remained quiescent. The last individual had recurrent symptoms prompting lacrimal gland biopsy that demonstrated chronic, nongranulomatous inflammation without monoclonality. The patient subsequently responded to periorbital steroid injection only to have a recurrent bout of inflammation after repeat dental cleaning. Another periorbital steroid injection resulted in resolution of inflammation. The authors propose that a subset of acute orbital inflammation may represent an autoimmune response triggered by dental manipulation. These cases are suggestive of an atypical variant of noninfectious, microbe-induced inflammation. PMID:22391741

Choe, Christina H; Eckstein, Lauren A; Vagefi, M Reza

373

Orbital Dzyaloshinskii-Moriya exchange interaction  

NASA Astrophysics Data System (ADS)

A superexchange calculation is performed for multiorbital band models with broken inversion symmetry. Orbital-changing hopping terms allowed by the symmetry-breaking electric field lead to a new kind of orbital exchange interaction closely resembling the Dzyaloshinskii-Moriya spin exchange. Inversion symmetry breaking as present in surfaces and interfaces and a strong on-site repulsion, but not the spin-orbit interaction, are the requirements to observe the proposed effect. The mean-field phase diagram exhibits a rich structure including anti-ferro-orbital, ferro-orbital, and both single and multiple spiral-orbital phases, in close analogy with the Skyrmion spin crystal phase recently discovered in thin-film chiral magnets.

Kim, Panjin; Han, Jung Hoon

2013-05-01

374

Precise Method of Orbit Height Determination  

NASA Astrophysics Data System (ADS)

The problem of satellite orbit determination is a very important one, you can determine the orbit height of a low Earth orbiting (LEO) artificial satellite by using the satellite's apparent travel when the satellite appears to be near your local zenith, Or for most precise between two points of observation in earth. By using the determined orbit height, you can also determine the approximate orbit period of the satellite, this method takes advantage of the fact that the satellite's true velocity can be seen when it is nearly overhead. This paper illustrate how to obtain the height of the satellite using two observers method and by using MATLAB program then comparing this method with one observer method and illustrating how to increase the accuracy and take the measurement not limited to the local zenith only, but to any place of the orbit if you have an estimated period time for the satellite also these calculations depends on the data from NASA site.

Elbanna, Ahmed

375

RHIC BPM system average orbit calculations  

SciTech Connect

RHIC beam position monitor (BPM) system average orbit was originally calculated by averaging positions of 10000 consecutive turns for a single selected bunch. Known perturbations in RHIC particle trajectories, with multiple frequencies around 10 Hz, contribute to observed average orbit fluctuations. In 2006, the number of turns for average orbit calculations was made programmable; this was used to explore averaging over single periods near 10 Hz. Although this has provided an average orbit signal quality improvement, an average over many periods would further improve the accuracy of the measured closed orbit. A new continuous average orbit calculation was developed just prior to the 2009 RHIC run and was made operational in March 2009. This paper discusses the new algorithm and performance with beam.

Michnoff,R.; Cerniglia, P.; Degen, C.; Hulsart, R.; et al.

2009-05-04

376

Determination and prediction of Magellan's orbit  

NASA Astrophysics Data System (ADS)

The Magellan spacecraft has been systematically mapping the surface of Venus since September 15, 1990, using a synthetic aperture radar. The spacecraft orbit about Venus is nearly polar, with an orbital period of 3.26 hours and periapsis altitude of 295 km. The radiometric measurements and the data reduction method used to determine and predict the spacecraft state are described. Orbit determination and prediction results are given for the first 146 days of mapping (through February 8, 1991, 60 percent of the first rotation of Venus). Orbit accuracy requirements of 150 meters in the radial position, and 1 km in the along-track and cross-track positions are shown to be met, but with exceptions. All error requirements were exceeded during a combined period of limited in-plane orbit observability due to earth-orbit relative geometry, and increased measurement noise due to superior conjunction.

Engelhardt, D. B.; McNamee, J. B.; Wong, S. K.; Bonneau, F. G.; Graat, E. J.; Haw, R. J.; Kronschnabl, G. R.; Ryne, M. S.

377

Surgical management of tumors involving the orbit.  

PubMed

IMPORTANCE Surgical treatment of orbital tumors is a complex task that requires thorough preparation and precise planning. Since a large variety of tumors of different origins, anatomical extents, and histologic subtypes affect the globe, no "1-size-fits-all" approach can be offered. OBJECTIVE To describe an integrative approach for the optimal surgical management of patients with orbital tumors based on a review of the literature and on our own experience at a high-volume cancer center. EVIDENCE REVIEW Peer-reviewed English-language literature and a single-center cohort of patients undergoing orbital exenteration with eye sparing, reconstruction, and preservation of orbital function. FINDINGS Surgical treatment of orbital tumors is a complex task that requires thorough preparation and precise planning that would be aided by an algorithm. CONCLUSIONS AND RELEVANCE We offer an algorithm that summarizes our approach toward the 2 main decision points of orbital surgery: extent of resection and method of reconstruction. PMID:23949361

Weizman, Noam; Horowitz, Gilad; Gil, Ziv; Fliss, Dan M

2013-08-01

378

Imaging of the normal and pathological orbit  

Microsoft Academic Search

.   Computerized techniques (CT and MRI) allow precise delineation of orbital anatomy and abnormalities. Orbital tumors are nicely\\u000a depicted by these methods; various examples are illustrated in this article, with discussion of the respective impact of CT\\u000a and MRI. Orbital inflammation and foreign bodies usually represent radiologic emergencies, prompting use of CT (frequently)\\u000a or MRI (occasionally). Digital subtraction angiography (DSA)

B. Duvoisin; F. E. Zanella; K. W. Sievers

1998-01-01

379

Orbits Around Black Holes in Triaxial Nuclei  

Microsoft Academic Search

We discuss the properties of orbits within the influence sphere of a\\u000asupermassive black hole (BH), in the case that the surrounding star cluster is\\u000anonaxisymmetric. There are four major orbit families; one of these, the pyramid\\u000aorbits, have the interesting property that they can approach arbitrarily\\u000aclosely to the BH. We derive the orbit-averaged equations of motion and show

David Merritt; Eugene Vasiliev

2010-01-01

380

The Orbital Maneuvering Vehicle - A new capability  

NASA Astrophysics Data System (ADS)

NASA's Orbital Maneuvering Vehicle (OMV) is a reusable remotely-controlled spacecraft for support of orbiting platforms through such functions as satellite delivery, satellite retrieval, satellite reboost, controlled satellite deorbit, satellite inspection, and subsatellite missions. The OMV will be a critical component of the Space Station program's operational scenario; it will be able to operate either from the Space Shuttle Orbiter or the Space Station, and can also be space-based. The maiden flight of the first OMV is projected for 1993.

Arcilesi, Charles J.; Holliman, Charles T.

1988-10-01

381

Neural networks and orbit control in accelerators  

SciTech Connect

An overview of the architecture, workings and training of Neural Networks is given. We stress the aspects which are important for the use of Neural Networks for orbit control in accelerators and storage rings, especially its ability to cope with the nonlinear behavior of the orbit response to `kicks` and the slow drift in the orbit response during long-term operation. Results obtained for the two NSLS storage rings with several network architectures and various training methods for each architecture are given.

Bozoki, E.; Friedman, A.

1994-07-01

382

Intracranial neurological injuries associated with orbital fracture.  

PubMed

We attempted to define the central nervous system (CNS) concomitants of various types of orbital fractures in children by reviewing the records of 95 inpatients with admission diagnoses including orbital fracture who presented to the Children's National Medical Center from 1987 through 1994. Patients were divided into three age groups: group I: 0-5 years; group II: 6-12 years; group III: older than 12 years. Orbital fractures were classified by location: roof alone (A); orbital roof plus another orbital wall (B), and orbital fractures sparing the roof (C). Mechanisms of injury included falls (F), motor vehicle accidents (M), and blunt injuries (S). Admission Glasgow Coma Scale (GCS), neurosurgical intervention, nature of associated intracranial injury, and presence of residual neurologic deficit were recorded. Group I included 38 patients, while groups II and III included 28 and 29, respectively. There were 61 boys and 34 girls. Most fractures confined to the roof occurred in group I patients (12 of 16 fractures; 75%). Twenty-four of the 38 group I patients (63%) sustained orbital fractures involving the roof compared to 12 (43%) and 6 (21%) in groups II and III, respectively. Children with orbital fractures involving the roof and another orbital wall, regardless of age, had lower admission GCS. Over half of type B fracture patients (19/26) were involved in motor vehicle accidents. Intracranial injuries were identified in 26 of the 73 patients (36%) whose CT included the brain. Fifteen of 26 patients (58%) with intracranial injuries sustained fractures involving the orbital roof, but only 3 of these had a type A fracture. Seven of the patients with intracranial injury required emergent neurosurgical procedures. Younger children with maxillofacial injury sparing the orbital roof appear more likely to have coexisting intracranial injury, as reflected by CT findings and GCS on admission, than their older cohorts with similar injuries. Fracture of more than one orbital wall greatly increases risk of concurrent intracranial injury in all age groups. PMID:9440496

Donahue, D J; Smith, K; Church, E; Chadduck, W M

1997-05-01

383

Bilateral orbital emphysema from compressed air injury  

Microsoft Academic Search

PURPOSE: To describe a patient who developed bilateral subconjunctival and orbital emphysema after an automobile tire explosion.METHOD: Case report.RESULTS: A 60-year-old man sustained bilateral ocular injury after a tire explosion. Ophthalmic examination disclosed bilateral subconjunctival air, with no visible conjunctival laceration. Computed tomography showed orbital emphysema, with no evidence of orbital fracture. Follow-up examination 2 weeks after the injury disclosed

Tina Li; Mahmood F Mafee; Deepak P Edward

1999-01-01

384

Animation: Kepler-11 and Six Orbiting Planets  

NASA Video Gallery

NASA's Kepler space telescope watches a star, Kepler-11. The star appears to blink in a pattern. It dims like clockwork as six "hands" of differing size orbit around it at different rates. Kepler-11 dims when its six orbiting planets cross between it and the Kepler spacecraft. Calculations show the planets are nested in circular orbits that lie in almost the same plane. Animation credit: NASA/Tim Pyle

Cathy Weselby

2011-01-24

385

Orbit correction techniques for a multipass linac  

SciTech Connect

The CEBAF accelerator includes a linac section which accelerates multiple beams with different energies. Problems arise when performing orbit correction, due to the fact that correction of higher energy passes disturb lower energy trajectories. Therefore, a perfect orbit correction cannot be obtained for all energy beams at the same time. We present methods and performance (using simulation results) for performing orbit corrections in such a system. Limitations to the correction method are also addressed. 2 refs., 5 figs.

Barry, A.; Bowling, B.; Kewisch, J.; Tang, J.

1990-09-01

386

Dynamics of the orbital cable system  

Microsoft Academic Search

The dynamical role of the cable in the proposed Orbital Cable System (OCS), consisting of a large powered vehicle in a 200-250-km orbit attached by a cable to a small probe in a 100-150-km orbit, is investigated analytically, and OCS deployment algorithms are developed. The dynamic effects of a realistic cable with mass, air drag, and elasticity are taken into

V. V. Beletskii; E. M. Levin

1983-01-01

387

Orbiter avionics aim at high reliability  

Microsoft Academic Search

Avionics and astrionics instrumentation, onboard computer system, and data displays of Orbiter are sketched. Information is provided on fly-by-wire guidance, radio altimeters, the Orbiter landing, mission timer (giving cumulative mission time readout and event timing), functions of the Shuttle Avionics Integration Laboratory (SAIL), and the HAL\\/S program language developed for the five Orbiter computers. Crossfeed of data between the five

K. J. Stein

1976-01-01

388

Orbital Debris and NASA's Measurement Program  

NASA Astrophysics Data System (ADS)

Since the launch of Sputnik in 1957, the number of manmade objects in orbit around the Earth has dramatically increased. The United States Space Surveillance Network (SSN) tracks and maintains orbits on over nine thousand objects down to a limiting diameter of about ten centimeters. Unfortunately, active spacecraft are only a small percentage ( ~ 7%) of this population. The rest of the population is orbital debris or ``space junk" consisting of expended rocket bodies, dead payloads, bits and pieces from satellite launches, and fragments from satellite breakups. The number of these smaller orbital debris objects increases rapidly with decreasing size. It is estimated that there are at least 130,000 orbital debris objects between one and ten centimeters in diameter. Most objects smaller than 10 centimeters go untracked! As the orbital debris population grows, the risk to other orbiting objects, most importantly manned space vehicles, of a collision with a piece of debris also grows. The kinetic energy of a solid 1 cm aluminum sphere traveling at an orbital velocity of 10 km/sec is equivalent to a 400 lb. safe traveling at 60 mph. Fortunately, the volume of space in which the orbiting population resides is large, collisions are infrequent, but they do occur. The Space Shuttle often returns to earth with its windshield pocked with small pits or craters caused by collisions with very small, sub-millimeter-size pieces of debris (paint flakes, particles from solid rocket exhaust, etc.), and micrometeoroids. To get a more complete picture of the orbital-debris environment, NASA has been using both radar and optical techniques to monitor the orbital debris environment. This paper gives an overview of the orbital debris environment and NASA's measurement program.

Africano, J. L.; Stansbery, E. G.

2002-05-01

389

Original and future cometary orbits. IV  

NASA Astrophysics Data System (ADS)

The values of the 'original' and 'future' reciprocal semimajor axes are calulcated for 36 recent osculating cometary orbits. The results are compared with the computations of Yabushita and Hasegawa (1989). Adjustments for deriving original and future orbits are given for nine other recent comets for which only parabolic orbit determinations are available. Specific attention is given to the physical comet pair 1987 XXX/1988 III.

Marsden, B. G.

1990-06-01

390

Deep reconditioning testing for near Earth orbits  

NASA Astrophysics Data System (ADS)

The problems and benefits of deep reconditioning to near Earth orbit missions with high cycle life and shallow discharge depth requirements is discussed. A simple battery level approach to deep reconditioning of nickel cadmium batteries in near Earth orbit is considered. A test plan was developed to perform deep reconditioning in direct comparison with an alternative trickle charge approach. The results demonstrate that the deep reconditioning procedure described for near Earth orbit application is inferior to the alternative of trickle charging.

Betz, F. E.; Barnes, W. L.

1984-09-01

391

The WISE in-orbit calibration  

Microsoft Academic Search

The Wide-field Infrared Survey Explorer mission will be executed by an earth-orbiting spacecraft carrying an infrared telescope cooled by a solid hydrogen cryostat. The purpose of the mission is to conduct an allsky survey at infrared wavelengths of 3.3, 4.7, 12 and 23 microns. The 7-month period of on-orbit operations includes one month of in-orbit checkout (IOC) and 6 months

Beth Fabinsky; Ingolf Heinrichsen; Amy Mainzer; Peter Eisenhardt

2008-01-01

392

A periodic table for black hole orbits  

SciTech Connect

Understanding the dynamics around rotating black holes is imperative to the success of future gravitational wave observatories. Although integrable in principle, test-particle orbits in the Kerr spacetime can also be elaborate, and while they have been studied extensively, classifying their general properties has been a challenge. This is the first in a series of papers that adopts a dynamical systems approach to the study of Kerr orbits, beginning with equatorial orbits. We define a taxonomy of orbits that hinges on a correspondence between periodic orbits and rational numbers. The taxonomy defines the entire dynamics, including aperiodic motion, since every orbit is in or near the periodic set. A remarkable implication of this periodic orbit taxonomy is that the simple precessing ellipse familiar from planetary orbits is not allowed in the strong-field regime. Instead, eccentric orbits trace out precessions of multileaf clovers in the final stages of inspiral. Furthermore, for any black hole, there is some point in the strong-field regime past which zoom-whirl behavior becomes unavoidable. Finally, we sketch the potential application of the taxonomy to problems of astrophysical interest, in particular its utility for computationally intensive gravitational wave calculations.

Levin, Janna [Department of Physics and Astronomy, Barnard College of Columbia University, 3009 Broadway, New York, New York 10027 (United States); Institute for Strings, Cosmology and Astroparticle Physics, Columbia University, New York, New York 10027 (United States); Perez-Giz, Gabe [Physics Department, Columbia University, New York, New York 10027 (United States)

2008-05-15

393

Orbital aspergillus infection diagnosed by FNAC.  

PubMed

Fungal infections of the orbit represent a small minority of orbital infections. However, due to the virulent nature of some of the fungal species, they can have a devastating effect on ocular functions. Most of these fungi are saprophytes, which cause opportunistic infections. Aspergillus is one such fungus that can cause infection at various sites in an immunosuppressed individual. Sinonasal aspergillus infection with orbital extension and orbital aspergillus infection progress relentlessly. They can have a precipitous clinical course resulting in total loss of vision. Fine needle aspiration cytology (FNAC) is rarely used as a preoperative diagnostic tool in the investigation of orbital mass lesions. Further, fungal infections of orbit are seldom diagnosed on FNAC. Two cases of fungal infection of the orbital and periorbital tissue diagnosed on FNAC are presented. A 50-year-old diabetic male presented with diminishing vision, pain, and forward protrusion of the left eye. On examination, he had upper eye lid fullness. A 55-year-old diabetic male presented with a swelling on the right upper eye lid. The patients were evaluated radiologically and then subjected to FNAC. The smears showed giant cells, histiocytes, epithelioid granulomas, and fungal hyphae. A diagnosis of fungal infection was arrived at which was subsequently confirmed by culture and biopsy. Orbital aspergillus infection can have a precipitous course. Computerized tomography and magnetic resonance imaging of the orbit provide crucial information. However, FNAC can help in making an early definitive diagnosis of fungal infection and thus obviate the need for a biopsy. PMID:21695805

Kuruba, Sree Lakshmi; Prabhakaran, Venkatesh C; Nagarajappa, A H; Biligi, Dayanand S

2010-11-09

394

Orbit stability of the ALS storage ring  

SciTech Connect

The Advanced Light Source (ALS) storage ring, a synchrotron light source of the third generation, is specified to maintain its electron orbit stable within one tenth of the rms beam size. In the absence of a dedicated orbit feed-back system, several orbit-distorting effects were investigated, aided by a new interactive simulation tool, the code TRACY V. The effort has led to a better understanding of the behavior of a variety of accelerator subsystems and in consequence produced a substantial improvement in day-to-day orbit stability.

Keller, R.; Nishimura, H.; Biocca, A. [and others

1997-05-01

395

Pterygomaxillary extension of orbital pseudotumor. Case report.  

PubMed

Idiopatic pseudotumor (IP) is a non-specific, non-neoplastic, inflammatory process without identifiable local or systemic causes. IP most commonly affects the orbit, comprising 5% to 8% of all orbital masses with occasional extension to other areas of the skull base. The ophthalmology literature has detailed reviews of IP as a space-occupying intraorbital lesion, but lesion involving only the skull base and sparing the orbit is exceptional. Understanding the presentation, work-up, and characteristics of the lesion is important for proper diagnosis and treatment. We report a rare case of orbital IP with extension into infratemporal fossa. Clinical and radiological findings and surgical approach are discussed. PMID:20444333

Ulivieri, S; Oliveri, G; Cerase, A; Menicacci, F; Motolese, P A; Motolese, I; Motolese, E; Miracco, C

2010-04-01

396

Orbital Aspergillosis: Voriconazole - The New Standard Treatment?  

PubMed Central

Background/Aim To describe a case of invasive orbital aspergillosis and evaluate treatments and outcomes. Methods A case report and review of orbital aspergillosis treatment with voriconazole in the English language literature. Conclusion Amphotericin B with debridement is the current standard of care for orbital aspergillosis; however, its prognosis is unfavorable. When compared to amphotericin B, voriconazole demonstrates a survival benefit, has less systemic toxicity, and is better tolerated by patients. While a prospective trial comparing amphotericin B to voriconazole in orbital aspergillosis is not feasible, there is evidence to support the use of voriconazole as primary therapy.

Ohlstein, Derek H.; Hooten, Claudia; Perez, Javier; Clark, Charles L.; Samy, Hazem

2012-01-01

397

Demonstration of Electrostatic Orbits in Weightlessness  

NASA Astrophysics Data System (ADS)

In August 2006, a team of students from Rhodes College performed an experiment in microgravity aboard NASA’s specialized C-9B aircraft known as the “Weightless Wonder.” The goal of the experiment was to establish an orbit between two electrically charged spheres. The similar forms of Newton’s Law of Gravitation and Coulomb’s Law suggest that such electrostatic orbits are possible. However, to our knowledge, an electrostatic orbit has not previously been demonstrated. This presentation will describe our experiment and show video footage of the electrostatic orbits that we achieved in weightlessness. Professor Brent Hoffmeister is the AAPT sponsor.

Janeski, John; Andring, K.; Banerjee, S.; Campbell, D.; Keedy, D.; Hoffmeister, B.; Quinn, S.

2006-12-01

398

Nebraska Astronomy Applet Project: Planetary Orbit Simulator  

NSDL National Science Digital Library

This simulation illustrates the physics of planetary orbits. The user can control the size and orbital path of the orbit. Each of Kepler's three laws and aspects of Newton's Law are each demonstrated. Velocity and acceleration vectors can be displayed, as well as the axes of the orbit. Instructor resources are available including student manuals, assessment materials, and a list of the assumptions used. This resource is part of a larger collection of online labs for introductory astronomy.See Related Materials for a link to the full collection.

Lee, Kevin M.

2007-12-20

399

Orbital and epicyclic frequencies of Maclaurin spheroids  

NASA Astrophysics Data System (ADS)

We present analytical formulae for the orbital and epicyclic frequencies in orbits around Maclaurin spheroids in Newtonian gravity. The Laplace equation for the gravitational potential implies that the orbital frequency squared is the arithmetic mean of the squares of the epicyclic frequencies, ? _r^2 + ? _z^2 = 2? _o^2. The radial epicyclic frequency has a maximum at radius r=?{2}ae for spheroid ellipticities e>1/?{2}, while for e = 0.834 583 18 it vanishes at the stellar equator (at r = a). For still larger ellipticities the innermost stable circular orbit (ISCO) is separated from the surface of the spheroid by a gap and has radius rms = 1.198 203 ae. The vertical epicyclic frequency is always larger than the orbital one, and always by a factor of ?{2} in the marginally stable orbit. The presence of periastron motion, nodal precession (whose sense is the same as in retrograde orbits in the Kerr metric) and of the ISCO makes the properties of orbital motion around Maclaurin spheroids analogous to those in the Kerr metric. We find that the condition for the existence of circular orbits in test-particle motion is ? _r^2 + ? _z^2 >0, equally for the Maclaurin spheroid and for the Kerr metric.

Klu?niak, W.; Rosi?ska, D.

2013-10-01

400

The Orbital-Selected Mott Phase of the Nondegenerate Two-Orbital Hubbard Model  

NASA Astrophysics Data System (ADS)

We use the dynamical mean-field theory to study the optical conductivity and orbital susceptibility of the nondegenerate two-orbital Hubbard model in the orbital-selective Mott phase. The optical conductivity of the wide band presents expectedly a nonzero Drude peak, while the localization character is observed for the optical conductivity of the narrow band. Particularly, a rapidly reverse shape in the orbital susceptibility emerges right at Fermi surface, implying the coexistence of the orbital ordering with the orbital-selected Mott phase. We also find that the orbital-selected Mott transition can be suppressed by the negative crystal field splitting. Applying the present findings to compound Ca2-xSrxRuO4, we demonstrate that the orbital-selected Mott phase can not survive in wide doping region from x=0.2 to 2.0.

Song, Yun

2012-02-01

401

Universal Procedures for Conversion of Orbital Elements to and from Position and Velocity (Unperturbed Orbits).  

National Technical Information Service (NTIS)

Universally applicable algorithms for converting from orbital elements to position and velocity, and vice versa are presented. Though the element set is universal, the algorithms distinguish internally between six types of orbit, three of them rectilinear...

R. H. Gooding

1987-01-01

402

Orbital Debris Environment for Spacecraft Designed to Operate in Low Earth Orbit.  

National Technical Information Service (NTIS)

The orbital debris environment model contained in this report is intended to be used by the spacecraft community for the design and operation of spacecraft in low Earth orbit. This environment, when combined with material dependent impact tests and spacec...

D. J. Kessler R. C. Reynolds P. D. Anz-Meador

1989-01-01

403

Independent Orbiter Assessment (IOA): Assessment of the Orbital Maneuvering Subsystem, Volume 2.  

National Technical Information Service (NTIS)

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Orbital Maneuvering System (OMS) hardware and electrica...

W. A. Haufler

1988-01-01

404

COMET C/2011 W3 (LOVEJOY): ORBIT DETERMINATION, OUTBURSTS, DISINTEGRATION OF NUCLEUS, DUST-TAIL MORPHOLOGY, AND RELATIONSHIP TO NEW CLUSTER OF BRIGHT SUNGRAZERS  

SciTech Connect

We describe the physical and orbital properties of C/2011 W3. After surviving perihelion passage, the comet was observed to undergo major physical changes. The permanent loss of the nuclear condensation and the formation of a narrow spine tail were observed first at Malargue, Argentina, on December 20 and then systematically at Siding Spring, Australia. The process of disintegration culminated with a terminal fragmentation event on December 17.6 UT. The postperihelion dust tail, observed for {approx}3 months, was the product of activity over <2 days. The nucleus' breakup and crumbling were probably caused by thermal stress due to the penetration of the intense heat pulse deep into the nucleus' interior after perihelion. The same mechanism may be responsible for cascading fragmentation of sungrazers at large heliocentric distances. The delayed response to the hostile environment in the solar corona is at odds with the rubble-pile model, since the residual mass of the nucleus, estimated at {approx}10{sup 12} g (equivalent to a sphere 150-200 m across) just before the terminal event, still possessed nontrivial cohesive strength. The high production rates of atomic oxygen, observed shortly after perihelion, are compatible with a subkilometer-sized nucleus. The spine tail-the product of the terminal fragmentation-was a synchronic feature, whose brightest part contained submillimeter-sized dust grains, released at velocities of up to 30 m s{sup -1}. The loss of the nuclear condensation prevented an accurate orbital-period determination by traditional techniques. Since the missing nucleus must have been located on the synchrone, whose orientation and sunward tip have been measured, we compute the astrometric positions of this missing nucleus as the coordinates of the points of intersection of the spine tail's axis with the lines of forced orbital-period variation, derived from the orbital solutions based on high-quality preperihelion astrometry from the ground. The resulting orbit gives 698 {+-} 2 yr for the osculating orbital period, showing that C/2011 W3 is the first member of the expected new, 21st-century cluster of bright Kreutz-system sungrazers, whose existence was predicted by these authors in 2007. From the spine tail's evolution, we determine that its measured tip, populated by dust particles 1-2 mm in diameter, receded antisunward from the computed position of the missing nucleus. The bizarre appearance of the comet's dust tail in images taken only hours after perihelion with the coronagraphs on board the SOHO and STEREO spacecraft is readily understood. The disconnection of the comet's head from the tail released before perihelion and an apparent activity attenuation near perihelion have a common cause-sublimation of all dust at heliocentric distances smaller than about 1.8 solar radii. The tail's brightness is strongly affected by forward scattering of sunlight by dust. From an initially broad range of particle sizes, the grains that were imaged the longest had a radiation-pressure parameter {beta} {approx_equal} 0.6, diagnostic of submicron-sized silicate grains and consistent with the existence of the dust-free zone around the Sun. The role and place of C/2011 W3 in the hierarchy of the Kreutz system and its genealogy via a 14th-century parent suggest that it is indirectly related to the celebrated sungrazer X/1106 C1, which, just as the first-generation parent of C/2011 W3, split from a common predecessor during the previous return to perihelion.

Sekanina, Zdenek; Chodas, Paul W., E-mail: Zdenek.Sekanina@jpl.nasa.gov, E-mail: Paul.W.Chodas@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

2012-10-01

405

Comet C/2011 W3 (Lovejoy): Orbit Determination, Outbursts, Disintegration of Nucleus, Dust-tail Morphology, and Relationship to New Cluster of Bright Sungrazers  

NASA Astrophysics Data System (ADS)

We describe the physical and orbital properties of C/2011 W3. After surviving perihelion passage, the comet was observed to undergo major physical changes. The permanent loss of the nuclear condensation and the formation of a narrow spine tail were observed first at Malargue, Argentina, on December 20 and then systematically at Siding Spring, Australia. The process of disintegration culminated with a terminal fragmentation event on December 17.6 UT. The postperihelion dust tail, observed for ~3 months, was the product of activity over <2 days. The nucleus' breakup and crumbling were probably caused by thermal stress due to the penetration of the intense heat pulse deep into the nucleus' interior after perihelion. The same mechanism may be responsible for cascading fragmentation of sungrazers at large heliocentric distances. The delayed response to the hostile environment in the solar corona is at odds with the rubble-pile model, since the residual mass of the nucleus, estimated at ~1012 g (equivalent to a sphere 150-200 m across) just before the terminal event, still possessed nontrivial cohesive strength. The high production rates of atomic oxygen, observed shortly after perihelion, are compatible with a subkilometer-sized nucleus. The spine tail—the product of the terminal fragmentation—was a synchronic feature, whose brightest part contained submillimeter-sized dust grains, released at velocities of up to 30 m s-1. The loss of the nuclear condensation prevented an accurate orbital-period determination by traditional techniques. Since the missing nucleus must have been located on the synchrone, whose orientation and sunward tip have been measured, we compute the astrometric positions of this missing nucleus as the coordinates of the points of intersection of the spine tail's axis with the lines of forced orbital-period variation, derived from the orbital solutions based on high-quality preperihelion astrometry from the ground. The resulting orbit gives 698 ± 2 yr for the osculating orbital period, showing that C/2011 W3 is the first member of the expected new, 21st-century cluster of bright Kreutz-system sungrazers, whose existence was predicted by these authors in 2007. From the spine tail's evolution, we determine that its measured tip, populated by dust particles 1-2 mm in diameter, receded antisunward from the computed position of the missing nucleus. The bizarre appearance of the comet's dust tail in images taken only hours after perihelion with the coronagraphs on board the SOHO and STEREO spacecraft is readily understood. The disconnection of the comet's head from the tail released before perihelion and an apparent activity attenuation near perihelion have a common cause—sublimation of all dust at heliocentric distances smaller than about 1.8 solar radii. The tail's brightness is strongly affected by forward scattering of sunlight by dust. From an initially broad range of particle sizes, the grains that were imaged the longest had a radiation-pressure parameter ? ~= 0.6, diagnostic of submicron-sized silicate grains and consistent with the existence of the dust-free zone around the Sun. The role and place of C/2011 W3 in the hierarchy of the Kreutz system and its genealogy via a 14th-century parent suggest that it is indirectly related to the celebrated sungrazer X/1106 C1, which, just as the first-generation parent of C/2011 W3, split from a common predecessor during the previous return to perihelion.

Sekanina, Zdenek; Chodas, Paul W.

2012-10-01

406

Analysis of orbital geometry and orbit maintenance of an Earth observation satellite  

NASA Astrophysics Data System (ADS)

An introduction to a recurring sun-synchronous orbit is given so as to choose adequately an orbit for Earth monitoring satellites. An analysis of choice criteria is made taking into account the hardware of the satellite and the mission constraints. For the orbit maintenance, an introduction to the perturbation is given, concluding with a qualitative analysis of the orbit correction maneuvers and a quantitative analysis in terms of the fuel consumption.

Matosdemedeiros, Valder

1987-08-01

407

Phonons with orbital angular momentum  

NASA Astrophysics Data System (ADS)

Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.

Ayub, M. K.; Ali, S.; Mendonca, J. T.

2011-10-01

408

Plasmons with orbital angular momentum  

SciTech Connect

Electron plasma waves carrying orbital angular momentum are investigated in an unmagnetized collisionless plasma composed of inertial electrons and static ions. For this purpose, the usual plasmon dispersion relation is employed to derive an approximate paraxial equation. The latter is analyzed with a Gaussian beam solution. For a finite angular momentum associated with the plasmon, Laguerre-Gaussian (LG) solutions are employed for solving the electrostatic potential problem which gives approximate solution and is valid for plasmon beams in the paraxial approximation. The LG potential determines the electric field components and energy flux of plasmons with finite angular momentum. Numerical illustrations show that the radial and angular mode numbers strongly modify the profiles of the LG potential.

Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Ali, S. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); National Centre for Physics, Shahdra Valley Road, Islamabad 44000 (Pakistan); Thide, B. [Swedish Institute of Space Physics, Angstroem Laboratory, P.O. Box 537, SE-751 21 Uppsala (Sweden)

2009-11-15

409

Phonons with orbital angular momentum  

SciTech Connect

Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.

Ayub, M. K. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Ali, S. [National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2011-10-15

410

ASCHOT - Astrophysical Schmidt Orbital Telescope  

NASA Astrophysics Data System (ADS)

The necessity for a wide-angle UV space telescope for astrophysical investigations is outlined. Some of the main scientific goals such as full-sky survey and massive study of UV emission of extragalactic and galactic objects, which may be achieved by the use of the Astrophysical Schmidt Orbital Telescope ASCHOT, are presented. The concept of the telescope design, its optical system, and its system of guidance are described. Electronic devices which may be used as detectors of UV emission in the telescope are considered. The limiting sensitivity of the telescope is estimated: it is about 24m for stellar objects at 1500 A. The control system of the telescope is briefly described.

Tovmasian, Kh. M.; Lorenz, H.; Priebe, A.; Richter, G. M.; Schmidt, K.-H.; Khodzhaiants, Iu. M.; Krmoian, M. N.; Isadzhanian, R. V.; Zakharian, A. Z.

1991-07-01

411

Benign fronto-orbital osteoblastoma arising from the orbital roof: case report and literature review  

Microsoft Academic Search

BackgroundOsteoblastoma is an uncommon benign osteogenic neoplasm that rarely involves the orbit. Intracranial and intraorbital extension causing neurologic and ophthalmologic symptoms and signs is very unusual. We report the case of an osteoblastoma of the orbital cavity with ethmoidal and anterior cranial fossa extension presenting as unilateral proptosis. Manifestations and management of this rare fronto-orbital lesion are discussed, and the

Ali Akhaddar; Miloudi Gazzaz; Mouna Rimani; Brahim Mostarchid; Ahmed Labraimi; Mohamed Boucetta

2004-01-01

412

Parametric studies and orbital analysis for an electric orbit transfer vehicle space flight demonstration  

Microsoft Academic Search

The Electric Insertion Transfer Experiment (ELITE) is an Air Force Advanced Technology Transition Demonstration which is being executed as a cooperative Research and Development Agreement between the Phillips Lab and TRW. The objective is to build, test, and fly a solar-electric orbit transfer and orbit maneuvering vehicle, as a precursor to an operational electric orbit transfer vehicle (EOTV). This paper

Edward R. Avila

1993-01-01

413

Admissible orbits in the Oort cloud and velocities on such orbits  

Microsoft Academic Search

In this paper we deal with determinations of: admissible orbits and ranges of orbital velocity in the cloud, extremal velocities at the distance r from the Sun. Moreover, in velocity space we consider the Or region in which there are located tips of velocity vectors for comets moving on admissible orbits.

Richard A. Serafin; A. Mickiewicz

1987-01-01

414

Nucleon Molecular Orbitals and the Transition Mechanism Between Molecular Orbitals in Nucleus-Nucleus Collisions.  

National Technical Information Service (NTIS)

The molecular orbitals of the nucleon(s) in nucleus-nucleus collisions are dynamically defined as a linear combination of nucleon single-particle orbits (LCNO) in a rotating frame by using the coupled-reaction-channel (CRC) theory. Nucleon molecular orbit...

B. Imanishi S. Misono W. von Oertzen H. Voit

1988-01-01

415

LROC - Lunar Reconnaissance Orbiter Camera  

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter Camera (LROC) is designed to address two of the prime LRO measurement requirements. 1) Assess meter and smaller-scale features to facilitate safety analysis for potential lunar landing sites near polar resources, and elsewhere on the Moon. 2) Acquire multi-temporal synoptic imaging of the poles every orbit to characterize the polar illumination environment (100 m scale), identifying regions of permanent shadow and permanent or near-permanent illumination over a full lunar year. The LROC consists of two narrow-angle camera components (NACs) to provide 0.5-m scale panchromatic images over a 5-km swath, a wide-angle camera component (WAC) to provide images at a scale of 100 and 400 m in seven color bands over a 100-km swath, and a common Sequence and Compressor System (SCS). In addition to acquiring the two LRO prime measurement sets, LROC will return six other high-value datasets that support LRO goals, the Robotic Lunar Exploration Program (RLEP), and basic lunar science. These additional datasets include: 3) meter-scale mapping of regions of permanent or near-permanent illumination of polar massifs; 4) multiple co-registered observations of portions of potential landing sites and elsewhere for derivation of high-resolution topography through stereogrammetric and photometric stereo analyses; 5) a global multispectral map in 7 wavelengths (300-680 nm) to characterize lunar resources, in particular ilmenite; 6) a global 100-m/pixel basemap with incidence angles (60-80°) favorable for morphologic interpretations; 7) sub-meter imaging of a variety of geologic units to characterize physical properties, variability of the regolith, and key science questions; and 8) meter-scale coverage overlapping with Apollo era Panoramic images (1-2 m/pixel) to document the number of small impacts since 1971-1972, to ascertain hazards for future surface operations and interplanetary travel.

Robinson, M. S.; Bowman-Cisneros, E.; Brylow, S. M.; Eliason, E.; Hiesinger, H.; Jolliff, B. L.; McEwen, A. S.; Malin, M. C.; Roberts, D.; Thomas, P. C.; Turtle, E.

2006-12-01

416

Lunar Reconnaissance Orbiter Mission and Spacecraft Design  

Microsoft Academic Search

Launched June 18, 2009, with its primary mission scheduled to end September 2010, NASA's Lunar Reconnaissance Orbiter will be the first observatory ever to spend an entire year orbiting and observing the Moon at a low altitude of just 50 km. The spacecraft carries a wide variety of scientific instruments and will provide an extraordinary opportunity to study the lunar

Craig R. Tooley; Martin B. Houghton; Richard S. Saylor; Cathy Peddie; David F. Everett; Charles L. Baker; Kristina N. Safdie

2010-01-01

417

CT diagnosis of orbital inflammation in children  

Microsoft Academic Search

The computed tomographic (CT) examination and medical records of fourteen children with orbital inflammatory disease were analyzed to determine which signs predicted or correlated with the clinical course. The preseptal space, the orbit and the sinuses are imaged simultaneously allowing accurate definition of the extent of disease. CT signs of inflammatory disease in each of these compartments are discussed.

Sandra K. Fernbach; T. P. Naidich

1981-01-01

418

Geostationary Satellite Orbit Analysis Program (OSOAP)  

Microsoft Academic Search

The paper describes a computer model which is capable of computing mutual interference among communications satellites in the geostationary satellite orbit. The model accesses a database of satellite orbital and system parameters and is composed of an interactive data retrieval element and an interference calculation element. The software package can support upwards of hundreds of satellite networks depending upon local

G. Hurt; H. Ng; H. Akima; C. Filippi

1986-01-01

419

Analysis and planning for precise orbital maneuvers  

Microsoft Academic Search

An orbit analysis is presented for an earth orbiting satellite equipped with navigation, guidance and control subsystems, whose mission requires precise maneuvers, retrieval of debris, or approaches to other satellites. Emphasis is placed on planning a practical maneuver sequence to avoid any collisions with target objectives during thruster failure by maximizing selection freedom of approach paths, considering recovery plans that

Megumi Suzaki; Kojiro Shoda; Masayuki Ikeuchi

1992-01-01

420

Optimal parking orbits for manned Mars missions  

NASA Astrophysics Data System (ADS)

This paper summarizes a Mars parking orbit optimization effort. This parking orbit study includes the selection of optimal elliptic Mars parking orbits that meet mission constraints and that include pertinent apsidal misalignment losses. Mars missions examined are for the opportunity years of 2014, 2016, and 2018. For these mission opportunities, it is shown that the optimal parking orbits depend on the year that the mission occurs and are coupled with the outbound, Mars stay, and return phases of the mission. Constraints included in the parking orbit optimization process are periapsis lighting angle (related to a daylight landing requirement), periapsis latitude (related to a landing latitude range requirement) and the vehicle Trans-Earth-Injection stage mass. Also, effects of mission abort requirements on optimal parking orbits are investigated. Off-periapsis maneuvers for Mars orbit capture were found to be cost effective in reducing the mission delta-V for the 2016 abort from Mars capture scenario. The total capture and departure delta-V was `split' between the capture maneuver and the departure maneuver to reduce the 2016 Mars departure delta-V to below the level of the corresponding stage of the 2014 baseline mission. Landing results are provided that show Mars landing site access from the optimal elliptic parking orbits for Mars excursion vehicles with low (0.2) and high (1.3 and 1.6) lift to drag ratio.

Cupples, Michael L.; Nordwall, Jill A.

421

A review of aeroassisted orbit transfer  

Microsoft Academic Search

The development of a theory of aeroassisted orbital plane change maneuvers and necessary equipment is traced and an assessment is made of potential applications. Synergetic plane changes are effected through a combination of aerodynamic and propulsive forces involving the dip of an orbiting vehicle into the atmosphere, performance of an aerodynamic turn using thrust if necessary, then reboosting into a

G. D. Walberg

1982-01-01

422

Venus Radar Mapper orbit accuracy analysis  

Microsoft Academic Search

Spacecraft orbital accuracies during the mapping phase of the Venus Radar Mapper Mission are the subject of this paper. The analysis presented describes the navigational strategy for the prime mission in support of mapping the planet Venus using a spacecraft deployed Synthetic Aperture Radar. Achievable orbital accuracies are shown to be limited by accuracy of interferometric data to be used.

S. N. Mohan; P. B. Esposito

1984-01-01

423

Spacecraft orbit determination using GPS navigation solutions  

Microsoft Academic Search

The orbit determination using the GPS navigation solutions for the KOMPSAT-1 spacecraft has been studied. The Cowell method of special perturbation theories was employed to develop a precision orbit propagation, and the perturbations due to geopotential, the gravity of the Sun and the Moon, solid Earth tides, ocean tides, the Earth's dynamic polar motion, solar radiation pressure, and atmospheric drag

Jae-Cheol Yoon; Byoung-Sun Lee; Kyu-Hong Choi

2000-01-01

424

Orbital characters of the iron-pnictides  

NASA Astrophysics Data System (ADS)

The orbital degree of freedom plays an important role in the physics of iron-based high-temperature superconductors and their parent compounds. For example, possible orbital ordering has been associated with the spin density wave, and we recently found that the superconducting gap sizes are different at the same Fermi momentum for two bands with different spatial symmetries. We studied the orbital characters of the electronic structure in optimally electron-doped BaFe1.85Co0.15As2 by exploiting the polarization-sensitivity of the orbitals in angle resolved photoemission spectroscopy. The orbital characters of the low energy electronic structure and Fermi surface in three dimensional momentum space are determined. Our results indicate that the previous orbital assignments of band structure calculations are just partially correct. Particularly, the contributions of the dxy and dx2-y2 orbitals were not right. Our results lay the foundation for constructing realistic microscopic models of iron-based superconductors. Furthermore, we studied the transport properties and electronic structure of magnetically detwinned NaFeAs, and AEFe2As2. We identify the roles of various orbitals in the spin density wave formation.

Feng, Donglai

2011-03-01

425

Congenital malignant rhabdoid tumor of the orbit  

Microsoft Academic Search

Malignant rhabdoid tumor is a rare and highly malignant renal tumor of infancy. Extrarenal tumors involving the orbit have been reported, but never at birth.1-5 The authors describe a primary malignant rhabdoid tumor of the orbit in a neonate who had massive unilateral proptosis at birth. Clinical, radiographic, and histologic features of the tumor are discussed.

D. Brian Stidham; Richard A. Burgett; Mary M. Davis; David A. Plager

1999-01-01

426

Transient oblong anisocoria and orbital surgery.  

PubMed

We present a rare case of transient oblong (segmental) anisocoria occurring at the time of limited orbital surgery. Observation of this previously undescribed phenomenon prompted us to review the relevant anatomy and physiology of the iris and the pharmacokinetics of lidocaine as it pertains to surgery in the region of the eyelids and the orbit. PMID:23154371

Goodwin, Isak A; Stotland, Mitchell A

2012-11-01

427

FAST IR ORBIT FEEDBACK AT RHIC.  

SciTech Connect

Mechanical low-{beta} triplet vibrations lead to horizontal jitter of RHIC beams at frequencies around 10 Hz. The resulting beam offsets at the interaction points are considered detrimental to RHIC luminosity performance. To stabilize beam orbits at the interaction points, installation of a fast orbit feedback is foreseen. A prototype of this system is being developed and tested. Recent results will be presented.

MONTAG, C.; MICHNOFF, R.; SATOGATA, T.; ET AL.

2005-05-16

428

Closed orbit correction in the SSC  

Microsoft Academic Search

A global correction scheme proposed for use in the SSC (Superconducting Super Collider) is described. Various features of the SSC lattice that impact the ability to correct the orbit are discussed. Typical results for the residual RMS closed orbit in the arc are calculated to be 0.65 mm with peak values of 3 mm

G. Bourianoff; B. Cole; H. Ferede; F. Pilat

1991-01-01

429

Laplacian Orbit Determination and Differential Corrections  

Microsoft Academic Search

Laplace's method is a standard for the calculation of a preliminary orbit. Certain modifications, briefly summarized, enhance its efficacy. At least one differential correction is recommended, and sometimes becomes essential, to increase the accuracy of the computed orbital elements. Difficult problems, lack of convergence of the differential corrections, for example, can be handled by total least squares or ridge regression.

Richard L. Branham

2005-01-01

430

Characteristics of Pellet Injuries to the Orbit  

Microsoft Academic Search

Purpose: To investigate the features of orbital injuries by pellets fired from the front. Design: Retrospective, 4 cases of pellet injuries. Methods: Five orbits of 4 patients who sustained pellet injuries received from the front were reviewed retrospectively. The course of injury and results were assessed. Radiological examinations were reviewed. The patients were evaluated between December 1996 and June 2004.

Turgut Yilmaz; Serdal Çelebi; Gürsoy Alagöz; Didem Serin; M. Akif Acar; M. Faik Özveren

2009-01-01

431

Europa Planetary Protection for Juno Jupiter Orbiter  

Microsoft Academic Search

NASA's Juno mission will launch in 2011 and explore the Jupiter system starting in 2016. Juno's suite of instruments is designed to investigate the gravitational fields, magnetic fields, and auroral regions and its low perijove polar orbit will allow it to explore portions of the Jovian environment never before visited. While the Juno mission is not orbiting or flying close

Douglas Bernard; Robert Abelson; Jennie Johannesen; Try Lam; William McAlpine; Laura Newlin

2010-01-01

432

The orbits of the retrograde Jovian satellites  

Microsoft Academic Search

A 2-Myr integration has been conducted for the sun-perturbed orbits of Saturn's four retrograde satellites, confirming that the apsis of Pasiphae is locked to that of Jupiter; its orbit is chaotic, with a 5000-yr inverse Liapunov exponent. The locking of two of these four satellites into this secular resonance, in addition to constraining theories of these satellites' formation, further suggests

Prasenjit Saha; Scott Tremaine

1993-01-01

433

[Orbital dysembryoplastic cyst at the conjunctival wall].  

PubMed

An 18-year-old female patient developed a mass in the superomedial angle of her left orbit. After evaluation, this tumor was surgically removed. A dysembryoplastic cyst lined with conjunctival epithelium was diagnosed by light microscopic examination. Clinical and pathological data are detailed. The characteristics of dysembryoplastic orbital cysts are reviewed. PMID:11139706

Meyer, A; Desjardins, L; D'hermies, F; Renard, G

2000-12-01

434

Orbitals: Some Fiction and Some Facts  

ERIC Educational Resources Information Center

|The use of electron orbitals in quantum theory and chemistry is discussed. Common misconceptions are highlighted. Suggestions are made how chemistry educators may describe orbitals in the first and second year college curriculum more accurately without introducing unwanted technicalities. A comparison is made of different ways of graphically…

Autschbach, Jochen

2012-01-01

435

Orbital debris removal and meteoroid deflection  

Microsoft Academic Search

Orbital debris in low-Earth orbit in the size range from 1 to 10 cm in diameter can be detected but not tracked reliably enough to be avoided by spacecraft. It can cause catastrophic damage even to a shielded spacecraft. With adaptive optics, a ground-based pulsed laser ablating the debris surface can produce enough propulsion in several hundred pulses to cause

Jonathan W. Campbell; Charles R. Taylor; Larry L. Smalley; Thomas Dickerson

1998-01-01

436

Orbit mechanics of deep space probes  

Microsoft Academic Search

Emphasized are orbits with high inclinations from the earth-moon orbital plane, with initial major axes oriented perpendicularly or inclined to the axis of syzygies and with period near that of the moon. The relation of this problem to the restricted problem of three and four bodies is discussed, showing the effects of luni-solar ephemerides versus the 'circular problem'. Various modifications

J. J. F. Liu; J. Segrest; V. Szebehely

1986-01-01

437

Optimal orbits for Mars atmosphere remote sensing  

Microsoft Academic Search

Most of the spacecrafts currently around Mars (or planned to reach Mars in the near future) use Sun-synchronous or near-polar orbits. Such orbits offer a very poor sampling of the diurnal cycle. Yet, sampling the diurnal cycle is of key importance to study Mars meteorology and climate. A comprehensive remote sensing data set should have been obtained by the end

Michel Capderou; François Forget

2004-01-01

438

Energy level diagrams for black hole orbits  

Microsoft Academic Search

A spinning black hole with a much smaller black hole companion forms a fundamental gravitational system, like a colossal classical analog to an atom. In an appealing if imperfect analogy with atomic physics, this gravitational atom can be understood through a discrete spectrum of periodic orbits. Exploiting a correspondence between the set of periodic orbits and the set of rational

Janna Levin

2009-01-01

439

THE ORBITAL DYNAMICS ENVIRONMENT OF 433 EROS  

Microsoft Academic Search

The dynamical environment experienced by the NEAR- Shoemaker spacecraft at Asteroid 433 Eros is discussed. From an orbital dynamics point of view the spacecraft was navigated in the most severely perturbed orbital environ- ment (relative to the standard 2-body problem) ever expe- rienced by a spacecraft. We discuss the regions relatively far from the asteroid, where solar effects are the

D. J. Scheeres

440

Radiation by Electrons in Large Orbits  

Microsoft Academic Search

By finding the points in the synchrotron magnetic cycle at which the time rate of change of electron orbit radius vanishes, the total electron energy loss per orbit revolution is measured. The results, for electron energies from 205 Mev to 280 Mev, are in excellent agreement with classical electromagnetic theory. The measurements have been extended to 318 Mev with reduced

Dale R. Corson

1953-01-01

441

Schwarzschild spacetime: measurements in orbiting space stations  

Microsoft Academic Search

The authors investigate the mechanical measurements which can be performed within a frame moving on spatially circular orbits in the Schwarzschild spacetime. The aim of this study is to provide an operational unambiguous definition of the inward direction to the centre of symmetry. To this purpose one needs two independent sets of measurements: the thrust necessary to keep the orbit

F. de Felice; S. Usseglio-Tomasset

1993-01-01

442

Orbit transfer rocket engine technology program  

Microsoft Academic Search

An advanced near term (1990's) space-based Orbit Transfer Vehicle Engine (OTVE) system was designed, and the technologies applicable to its construction, maintenance, and operations were developed under Tasks A through F of the Orbit Transfer Rocket Engine Technology Program. Task A was a reporting task. In Task B, promising OTV turbomachinery technologies were explored: two stage partial admission turbines, high

N. B. Gustafson; T. J. Harmon

1993-01-01

443

Inverse-Square Orbits: A Geometric Approach.  

ERIC Educational Resources Information Center

|Presents a derivation of Kepler's first law of planetary motion from Newtonian principles. Analogus derivations of the hyperbolic and parabolic orbits of nonreturning comets and the hyperbolic orbit for a particle in a repulsive inverse-square field are also presented. (HM)|

Rainwater, James C.; Weinstock, Robert

1979-01-01

444

Long-term stability of horseshoe orbits  

NASA Astrophysics Data System (ADS)

Unlike Trojans, horseshoe co-orbitals are not generally considered to be long-term stable. As the lifetime of Earth's and Venus's horseshoe co-orbitals is expected to be about a Gyr, we investigated the possible contribution of late-escaping inner planet co-orbitals to the lunar Late Heavy Bombardment. Contrary to analytical estimates, we do not find many horseshoe objects escaping after the first 100 Myr. In order to understand this behaviour, we ran a second set of simulations featuring idealized planets on circular orbits with a range of masses. We find that horseshoe co-orbitals are generally long lived (and potentially stable) for systems with primary-to-secondary mass ratios larger than about 1200. This is consistent with the results of Laughlin & Chambers for equal-mass pairs of co-orbital planets and the instability of Jupiter's horseshoe companions. Horseshoe orbits at smaller mass ratios are unstable because they must approach within 5 Hill radii of the secondary. In contrast, tadpole orbits are more robust and can remain stable even when approaching within 4 Hill radii of the secondary.

?uk, Matija; Hamilton, Douglas P.; Holman, Matthew J.

2012-11-01

445

Orbit: an optimizing compiler for scheme  

Microsoft Academic Search

Orbit was an optimizing compiler for T, a dialect of Scheme. Its aggressive use of CPS conversion, novel closure representations, and efficient code generation strategies made it the best compiler for a Scheme dialect at the time and for many years to come. The design of T and Orbit directly spawned six PhD theses and one Masters thesis, and influenced

David Kranz; Richard Kelsey; Jonathan Rees; Paul Hudak; James Philbin; Norman Adams

2004-01-01

446

Local and global behavior near homoclinic orbits  

Microsoft Academic Search

We study the local behavior of systems near homoclinic orbits to stationary points of saddle-focus type. We explicitly describe how a periodic orbit approaches homoclinicity and, with the help of numerical examples, discuss how these results relate to global patterns of bifurcations.

Paul Glendinning; Colin Sparrow

1984-01-01

447

Spin-orbital texture in topological insulators.  

PubMed

For three-dimensional topological insulators in the Bi2Se3 family, topological surface states with p(z) orbitals have a left-handed spin texture for the upper Dirac cone and a right-handed spin texture for the lower Dirac cone. In this work, we predict a new form of the spin-orbital texture associated with the p(x) and p(y) orbitals. For the upper Dirac cone, a left-handed (right-handed) spin texture is coupled to the "radial" ("tangential") orbital texture, whereas for the lower Dirac cone, the coupling of spin and orbital textures is the exact opposite. The "tangential" ("radial") orbital texture is dominant for the upper (lower) Dirac cone, leading to the right-handed spin texture for the in-plane orbitals of both the upper and lower Dirac cones. A spin-resolved and photon polarized angle-resolved photoemission spectroscopy experiment is proposed to observe this novel spin-orbital texture. PMID:23971598

Zhang, Haijun; Liu, Chao-Xing; Zhang, Shou-Cheng

2013-08-05

448

Quantum wave packets on Kepler elliptic orbits  

Microsoft Academic Search

Wave-packet solutions of the Schrödinger equation for the Coulomb potential are obtained that travel along classical elliptic orbits of fixed mean eccentricity and angular momentum. These wave packets are coherent states that have minimal quantum fluctuations in the noncommuting components of the Lenz vector in the plane of the orbit. For large quantum numbers the asymptotic form of the wave

Michael Nauenberg

1989-01-01

449

Generation of Nep Heliocentric Trajectory Data.  

National Technical Information Service (NTIS)

A study, designed to generate representative nuclear electric propulsion data for rendezvous missions to the comet Encke using the variational calculus program HILTOP, is presented. Other purposes of the study include a comparison of the HILTOP data with ...

J. L. Horsewood K. B. Brice

1972-01-01

450

Count Bowell at record heliocentric distance  

Microsoft Academic Search

New observations of Comet Bowell at the record distance of 13.6 AU are presented. An extended coma is present, the size of which is consistent with the same slow expansion rate of roughly 1 m\\/s detected around perihelion. The cross-section of the solid grains within the central 10 arcsec of the coma has decreased by over an order of magnitude

K. J. Meech; David Jewitt

1987-01-01

451

Copernicus, medicine, and the heliocentric concept.  

PubMed

With his back to the academically poorly oriented times of medieval Europe, Copernicus, the medical man, led the world into a concept of infinite space. His revolutionary concepts of astrophysics formed a buttress for the efforts of his successors. He looked to the stars, but he also had time to look at and help man. PMID:6351269

Miller, J M

1983-09-01

452

M-Dwarfs at Large Heliocentric Distances  

Microsoft Academic Search

We present an analysis of the faint M star population seen as foreground\\u000acontaminants in deep extragalactic surveys. We use space-based data to separate\\u000asuch stars from high redshift galaxies in a publically-available dataset, and\\u000aconsider the photometric properties of the resulting sample in the optical and\\u000ainfrared. The inferred distances place these stars well beyond the scale height\\u000aof

Elizabeth R. Stanway; Malcolm N. Bremer; Matthew D. Lehnert; John J. Eldridge

2007-01-01

453

The heliocentric system and general relativity theory  

Microsoft Academic Search

Parallels are drawn between the gradual acceptance and verification of Copernican theory and, in recent times, of Einstein's general theory of relativity. The relationship between Mach's principle and general relativity is discussed. Recent experimental verifications of general relativity are described, and some fundamental concepts concerning relativistic effects in stars are outlined.

V. L. Ginzburg

1974-01-01

454

Designs of optimal free-return orbit for moon landing  

Microsoft Academic Search

The paper designs the transfer orbit of the lunar landing from the low earth orbit to the low moon orbit based on the patched-conic technique. The equations of orbital parameters are established by utilizing the conservation of moment of momentum. Considering the optimization of the consumption of energy and time, the paper constructs the corresponding optimization problems to the orbital

Liu Xinglong; Dun Guangren

2007-01-01

455

Numerical experiments on planetary orbits in double stars  

Microsoft Academic Search

This is a numerical study of orbits in the elliptic restricted three-body problem concerning the dependence of the critical orbits on the eccentricity of the primaries. They are defined as being the separatrix between stable and unstable single periodic orbits. As our results are adapted to the existence of planetary orbits in double stars we concentrated first on the P-orbits

R. Dvorak

1984-01-01

456

The solar Poynting–Robertson effect on particles orbiting Solar System bodies: Circular orbits  

NASA Astrophysics Data System (ADS)

The Poynting–Robertson effect from sunlight impinging directly on a particle which orbits a Solar System body (planet, asteroid, comet) is considered from the Sun's rest frame. There appear to be no significant first-order terms in Vb/c for circular orbits, where Vb is the body's speed in its orbit about the Sun and c is the speed of light, when the particle's orbital semimajor axis is much smaller than the body's orbital semimajor axis about the Sun as is mainly the case in the Solar System.

Rubincam, David Parry

2013-11-01

457

Safety of titanium mesh for orbital reconstruction.  

PubMed

During the past several decades, the standard of care for orbital reconstruction after trauma has been autogenous bone grafts. Complications of bone grafts, including donor site morbidities such as scar alopecia and graft resorption with delayed enophthalmos, have inspired an interest in the use of alloplastic substitutes such as titanium. Titanium's role in orbital reconstruction was limited originally to small orbital defects, and as an adjunct to bone grafts. More recently, clinical studies have documented the sole use of titanium mesh to reconstruct large orbital defects. This study sought to document further the safety and efficacy of titanium mesh in reconstructing large orbital defects after facial trauma, with more extensive follow-up compared with previous studies. In the current study, 55 patients with 67 orbital fractures underwent orbital reconstruction with titanium mesh over a 5-year period. Associated fractures were reduced anatomically and fixed rigidly. For the analysis, 44 patients with 56 orbital fractures had adequate follow-up (mean, 44 months). An abscess developed in one patient who received high-dose steroids for 72 hours before reconstruction. She was treated with broad-spectrum intravenous antibiotics and bedside incision and drainage, and did not require removal of the titanium mesh. No patient in the current series required removal of the titanium mesh. A single case of uncorrected enophthalmos was treated with bone grafting rather than mesh revision. Large orbital defects can be reconstructed using titanium mesh with good functional results and minimal risk for infection. This study covered the authors' first 5 years using titanium. They have now used titanium mesh in orbital reconstructions for more than 10 years, without any additional cases of infection. PMID:11773723

Gear, Andrew J L; Lokeh, Adam; Aldridge, Jeffrey H; Migliori, Mark R; Benjamin, Charles I; Schubert, Warren

2002-01-01

458

Gravity and Orbits: Gravitational Force  

NSDL National Science Digital Library

This Science Object is the second of three Science Objects in the Gravity and Orbits SciPack. It investigates the variables that influence gravitational forces acting on objects. Mass is a measure of the amount of matter that makes up an object (regardless of where that object is located) and weight is a measure of the gravitational force acting on an object. The strength of the gravitational force between masses is proportional to the product of the masses and inversely proportional to the square of the distance between them. Gravity will cause all objects at the same distance from Earth's surface to fall toward Earth with the same acceleration regardless of their mass. Learning Outcomes:� Identify variables that affect the strength of the gravitational force acting between any two objects.� Provide a quantitative description of the relationship between the mass of two object and the gravitational force between them.� Provide a qualitative description of the relationship between the mass of two objects and the gravitational force between them.� Provide a quantitative description of the relationship between distance and gravitational force. � Provide a qualitative description of the inverse square relationship.� Recognize the effect of air resistance on object falling near Earth's surface, and thus be able to explain why two objects with different masses, at the same distance from Earth's surface, will have equal accelerations if air resistance is ignored.

National Science Teachers Association (NSTA)

2006-11-01

459

Gravity and Orbits: Universal Gravitational  

NSDL National Science Digital Library

This Science Object is the first of three Science Objects in the Gravity and Orbits SciPack. It provides an understanding of gravitational forces associated with all objects that have mass. Every object exerts a gravitational force on every other object. The force is hard to detect unless at least one of the objects has a lot of mass. Any two objects will exert an equal gravitational force (in opposite directions) on one another. Gravity is the force behind the falling rain and flowing rivers, and is responsible for pulling the matter that makes up planets and stars toward their centers to form spheres. Learning Outcomes:� Identify gravity as an attractive force associated with all objects, including less intuitive examples (such as soda cans and pencils).� Recognize some examples of phenomena that are the result of Earth's gravity and objects and structures in the universe in general.� Reject the idea that Earth's gravity is an effect of air pushing down toward the surface.� Recognize that gravitational force does not require air (or any other substance) as a medium to act.� Describe gravitational force as a mutual attraction, rather than as one object pulling on another.

National Science Teachers Association (NSTA)

2006-11-01

460

Are there atomic orbitals in a molecule?  

PubMed

Effective atomic orbitals (AOs) have been calculated by the method of the "fuzzy atoms" analysis by using the numerical molecular orbitals (MOs) obtained from plane-wave DFT calculation, i.e., without introducing any atom-centered functions. The results show that in the case of nonhypervalent atoms there are as many effective AOs with non-negligible occupation numbers, as many orbitals are in the classical minimal basis set of the given atom. This means that, for nonhypervalent systems, it is possible to present the MOs as sums of effective atomic orbitals that resemble very much the atomic minimal basis orbitals of the individual atoms (or their hybrids). For hypervalent atoms some additional orbitals basically of d-type are also of some importance; they are necessary to describe the back-donation to these positive atoms. It appears that the d-type orbitals play a similar role also for strongly positive carbon atoms. The method employed here is also useful to decide whether the use of polarization functions of a given type is a matter of conceptual importance or has only a numerical effect. PMID:21699211

Mayer, I; Bakó, I; Stirling, A

2011-06-23

461

The atomic orbitals of the topological atom.  

PubMed

The effective atomic orbitals have been realized in the framework of Bader's atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These correspond to atomic hybrids that closely resemble the core and valence shells of the atom. The occupation numbers of the remaining effective orbitals are almost negligible, except for atoms with hypervalent character. In addition, the molecular orbitals of a calculation can be exactly expressed as a linear combination of this orthonormalized set of numerical atomic orbitals, and the Mulliken population analysis carried out on this basis set exactly reproduces the original QTAIM atomic populations of the atoms. Approximate expansion of the molecular orbitals over a much reduced set of orthogonal atomic basis functions can also be accomplished to a very good accuracy with a singular value decomposition procedure. PMID:23758358

Ramos-Cordoba, Eloy; Salvador, Pedro; Mayer, István

2013-06-01

462

Periodic orbits and escapes in dynamical systems  

NASA Astrophysics Data System (ADS)

We study the periodic orbits and the escapes in two different dynamical systems, namely (1) a classical system of two coupled oscillators, and (2) the Manko-Novikov metric which is a perturbation of the Kerr metric (a general relativistic system). We find their simple periodic orbits, their characteristics and their stability. Then we find their ordered and chaotic domains. As the energy goes beyond the escape energy, most chaotic orbits escape. In the first case we consider escapes to infinity, while in the second case we emphasize escapes to the central "bumpy" black hole. When the energy reaches its escape value, a particular family of periodic orbits reaches an infinite period and then the family disappears (the orbit escapes). As this family approaches termination it undergoes an infinity of equal period and double period bifurcations at transitions from stability to instability and vice versa. The bifurcating families continue to exist beyond the escape energy. We study the forms of the phase space for various energies, and the statistics of the chaotic and escaping orbits. The proportion of these orbits increases abruptly as the energy goes beyond the escape energy.

Contopoulos, George; Harsoula, Mirella; Lukes-Gerakopoulos, Georgios

2012-07-01

463

Neuro-ophthalmology of orbital disease.  

PubMed

In this chapter the presentation and management of common orbital diseases are discussed. An accurate clinical history and assessment are essential, with computed tomography being the imaging of choice. Magnetic resonance imaging provides detail of intrinsic optic nerve disease and orbital apical or intracranial pathology, and ultrasonography is valuable in assessing anterior orbital masses, in particular vascular lesions. Inflammatory lesions require a tissue biopsy before immunosuppression is instituted. Exceptions to this principle are scleritis, myositis, thyroid eye disease, and characteristic orbital apex syndrome, in which delay in immune suppression may jeopardize visual outcome. The term "orbital pseudotumor" is now obsolete. The management of active thyroid eye disease includes immunosuppression and low-dose orbital radiotherapy. Urgent orbital decompression is indicated in the presence of nonresponsive optic neuropathy, and inactive disease is managed by decompression for exophthalmos, and correction of muscle imbalance and lid retraction. Subacute lacrimal gland inflammation, unresponsive to a few weeks of nonsteroidal treatment, may be due to underlying carcinoma and a specialist opinion should be sought without delay. Pleomorphic adenoma, with typical features on imaging, should always be excised intact to avoid subsequent pervasive malignant disease. PMID:21601077

Rose, Geoffrey E; Verity, David H

2011-01-01

464

The atomic orbitals of the topological atom  

NASA Astrophysics Data System (ADS)

The effective atomic orbitals have been realized in the framework of Bader's atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These correspond to atomic hybrids that closely resemble the core and valence shells of the atom. The occupation numbers of the remaining effective orbitals are almost negligible, except for atoms with hypervalent character. In addition, the molecular orbitals of a calculation can be exactly expressed as a linear combination of this orthonormalized set of numerical atomic orbitals, and the Mulliken population analysis carried out on this basis set exactly reproduces the original QTAIM atomic populations of the atoms. Approximate expansion of the molecular orbitals over a much reduced set of orthogonal atomic basis functions can also be accomplished to a very good accuracy with a singular value decomposition procedure.

Ramos-Cordoba, Eloy; Salvador, Pedro; Mayer, István

2013-06-01

465

The Anomalous Orbital Motion Of Mab Explained  

NASA Astrophysics Data System (ADS)

Showalter and Lissauer (2003) reported the discovery of two previously unknown inner satellites of Uranus (Mab and Cupid), using data from the Hubble Space Telescope (HST). Subsequently, they announced the discovery of an outer ring system composed of the ?-ring and the ?-ring (Showalter and Lissauer, 2006). They showed that the orbit of Mab, embedded in the ?-ring, is not well understood, after comparing its orbital position derived from Voyager flyby data (1986) to HST data (2003-2006). The observed positions were compared with a Keplerian orbital model that included the gravitational flattening of Uranus. Although this model works well for nine other Uranian moons, for Mab the fitting errors are six times larger. Mab is relatively bright in the data and well isolated from the other moons, suggesting that the measurement errors should not be large. Hence, the magnitude of the orbit fit residual seems to indicate that we are currently overlooking an essential part of the dynamics that determines the orbit of Mab. It is clear from these discoveries that Mab and the ?-ring are intriguing, constituting "a densely packed, rapidly varying, and possibly unstable dynamical system." We investigated the nature of Mab's anomalous orbital motion, which has thus far remained unexplained. The dynamical effects we simulated result from the interaction of Mab with a hypothetical ring of undetected moonlets in its neighborhood. We explored the effects of varying the characteristics of such a ring (mass and orbital-element distribution) on Mab's orbital motion. From these results we are able to highlight a number of interesting dynamical regimes. In particular, our simulations reveal the important role that perturbers occupying horseshoe orbits might play in determining the perturbations experienced by Mab. Further studies will be conducted to investigate the long-term stability of a possible perturber ring.

Kumar, Kartik; de Pater, I.; Showalter, M. R.

2012-10-01

466

About Hohmann Transfer with Orbital Plane Change  

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): We analitically studied the generalized Hohmann orbital transfer by considering non coplanar and elliptical orbits instead of planar and circular. It was done in order to find the transfer orbit that minimizes the energy and therefore the missing mass of a satellite through the application of two non-tangential impulses. We found an analytical expression that leads to minimize the fuel cost after assuming some reasonable physical constraints. Finally, we discuss some possible configurations and applications to our model.

Rincón, Ángel; Rojo, P.; Diaz, S.

2013-05-01

467

EDITORIAL: XVI Brazilian Colloquium on Orbital Dynamics  

NASA Astrophysics Data System (ADS)

The XVI Brazilian Colloquium on Orbital Dynamics was held from 26–30 November 2012, at the Biazi Grand Hotel, Serra Negra, São Paulo, Brazil. The Brazilian Colloquia on Orbital Dynamics are scientific events that occur bi-annually and are designed to develop those areas of research in celestial mechanics, orbital dynamics, planetary science, fundamental astronomy, aerospace engineering, and nonlinear systems and chaos. The meeting has been held for 30 years and it brings together researchers, professors and students from South American and also from other continents. Acknowledgements National Council for Scientific and Technological Development – CNPq Coordination for the Improvement of Higher Level – CAPES São Paulo Research Foundation - FAPESP

de Melo, Cristiano F.; Macau, Elbert E. N.; Prado, Antonio B. A.; Hetem Jnr, Annibal

2013-10-01

468

Analysis of expendable electric orbit transfer vehicles  

NASA Astrophysics Data System (ADS)

This analysis estimated the Low Earth Orbit (LEO) to Geostationary Orbit (GEO) transfer times for various payloads and electric propulsion systems using the Titan IV launch vehicle. The results indicate that, based on current and projected technology, a minimum payload requirement of 5,800 (kg) delivered to GEO off a Titan IV, expendable EOTVs have limited value for supporting USAF heavy payload orbit transfer missions in less than 100 days. However, if trip time is permitted to increase beyond 100 days, the benefits realized by using electric propulsion are significant.

Schmidt, W. M.

1990-07-01

469

An ion propulsion orbit manoeuvring vehicle  

NASA Astrophysics Data System (ADS)

It is shown that the concept of a reusable ion propulsion orbit maneuvering vehicle (OMV) can fulfill two particular orbital dynamics needs for the coming decades. On is the boosting of nonoperational satellites out of GEO in order to reduce GEO crowding and frequency transmission crosstalk. The other is the ability to maneuver certain satellites and other orbital debris out of the area in which the Space Station is to be located. The vehicle is flexible in operation, far less expensive than a chemical OMV, and requires very little fuel and maintenance.

Holdaway, R.; Flaherty, M.

1990-10-01

470

The orbital evolution of binary galaxies  

NASA Astrophysics Data System (ADS)

We present the results of self-consistent numerical simulations performed to study the orbital circularization of binary galaxies. We have generalized a previous model (Junqueira & de Freitas Pacheco 1994) and confirmed partially their results. The orbital evolution of pairs of galaxies is faster when we consider interacting pairs with contacting ``live'' galaxy halos but the circularization time remains larger than the Hubble time. Besides, the time behavior of the orbits has changed in comparison with previous work because of tidal forces and dynamical friction acting on the halos.

Chan, R.; Junqueira, S.

2001-02-01

471

THE PYTHON SHELL FOR THE ORBIT CODE  

SciTech Connect

A development of a Python driver shell for the ORBIT simulation code is presented. The original ORBIT code uses the SuperCode shell to organize accelerator-related simulations. It is outdated, unsupported, and it is an obstacle to future code development. The necessity and consequences of replacing the old shell language are discussed. A set of core modules and extensions that are currently in PyORBIT are presented. They include particle containers, parsers for MAD and SAD lattice files, a Python wrapper for MPI libraries, space charge calculators, TEAPOT trackers, and a laser stripping extension module.

Shishlo, Andrei P [ORNL; Gorlov, Timofey V [ORNL; Holmes, Jeffrey A [ORNL

2009-01-01

472

Orbital involvement in Bing-Neel syndrome.  

PubMed

Bing-Neel syndrome (BNS) is defined as intracranial involvement of Waldenström macroglobulinemia (WM). Few cases of orbital involvement have been reported. A 51-year-old man with a history of WM developed bilateral orbitopathy and optic neuropathy. Orbital biopsy, cerebrospinal fluid studies, and neuroimaging confirmed the diagnosis of BNS involving the orbital soft tissues, optic nerves, meninges, and cauda equina. The neuro-ophthalmic manifestations resolved after parenteral and intrathecal chemotherapy in addition to autologous stem cell transplantation. The rare neuro-ophthalmic manifestations of BNS may require a multifaceted approach to therapy. PMID:20548243

Stacy, Rebecca C; Jakobiec, Frederick A; Hochberg, Fred H; Hochberg, Ephraim P; Cestari, Dean M

2010-09-01

473

Radar observations in low earth orbit  

NASA Astrophysics Data System (ADS)

This paper presents an overview on radar techniques for the observation of space debris in low Earth orbits which were developed at FGAN in the frame of DARA and ESA/ESOC study contracts for the employment of the Tracking and Imaging Radar (TIRA) system in the past five years. For space debris observations TIRA is mainly operated in two different modes: In a tracking mode and in a beam-park mode of operation. Methods and algorithms were developed to analyse raw radar data, to compute radar images, and to estimate physical characteristics of space objects like size, shape, attitude, orbit, orbital lifetime, ballistic coefficient, mass, and material composition.

Mehrholz, Dieter

1997-05-01